Recent Patents on Materials Science - Volume 3, Issue 2, 2010

To perform pressure measuring or monitoring under harsh environments, robust materials are in demand. The outstanding properties of wide-bandgap semiconductors (WBGS) such as silicon carbide, III-V nitrides, and diamond offer great potential for these materials as micro-electro-mechanical-system (MEMS) pressure sensors toward such purpose. The variations in materials growth and surface/bulk machining technologies lead to the development of pressure sensors using these materials stays at different stages. The technologies for MEMS pressure sensors based on silicon carbide are established, and those of III-V nitrides are still under development. In contrast, the application of diamond in pressure sensors is far behind other wide-bandgap semiconductors. By using WBGS materials, the MEMS pressure sensors can operate at 600°C or higher for more than one hundred hours. In this paper, the recent patents on the progress of micro-machined pressure sensors based on the wide-bandgap semiconductors will be reviewed.

Most materials expand on heating and contract on cooling. However, an increasing number of materials with negative thermal expansion (NTE) have been discovered in recent years. In this article, we review the patents related to the synthesis and applications of several important families of negative thermal expansion materials. Particular attention has been paid to the families of NTE materials with open framework structures consisting of corner-sharing polyhedra that are relatively rigid but flexible in rotation such as A(MO4)2 (A=Zr, Hf or combinations of them; M=W, Mo or combinations of them), A4+P2O7 (A is an element with valance of +4, A and P can also be partially replaced by other elements with charge balance), A2(MO4)3 (A=Sc, Y, Al, Lu etc. and may be partially substituted by other elements) and Zr2P2WO12, Ca1-xMxZr4P6O24 (M= Sr, Ba, Mg). Some patents with the family of NTE materials with a framework structure consisting of relatively soft polyhedra connected by stiff cyanide bridges such as Zn(CN)2 and Cd(CN)2, etc. and the family of the NTE materials of perovskite manganese nitrides whose NTE is driven by magnetovolume effect are also involved. The most important applications of the NTE materials are to compensate for undesired positive expansion of other materials, creating ceramics, composites or devices with controllable overall negative, zero or positive coefficient of thermal expansion. The patents related to these applications are reviewed. Some problems existing with particular materials or applications are commented.

Being versatile in nature the clays are being extensively explored for their use in developing selective adsorbent materials, which can be further applied for selective gas separation and purification. In this article, a small preface to different categories of clay based materials has been made and further some selected patents, involving the use of claybased materials for selective gas separation and purification have been reviewed. Amongst different applications clays have widely been used either as a binder, to support microporous active adsorbent in composite materials or as chemically modified selective adsorbent. A range of composite materials with zeolites, silica, activated carbon and modified clays as well as their corresponding applications has been detailed. These materials have gained much attention for their frequent use in the process of natural gas purification, O2 and N2 separation from air, and separation of toxic or valuable gases from exhaust. In most cases, the developed materials were employed with Pressure swing adsorption or Thermal swing adsorption techniques.

In the last decade, number of patents claiming degradable biomaterials have been increasing worldwide. This novel class of biomaterials is intended to be used for implants having temporary function like coronary stents. Biodegradable stents are expected to provide a temporary opening for narrowed arterial vessels until they remodel and progressively disappear thereafter. Metallic biodegradable stents have recently been advanced to pre-clinical tests in humans after their first introduction in early 2000s. By referring to patents and journal publications, this article will review the metallic biodegradable stents, highlighting materials and processes. Their current and future developments will be discussed.

Synergistic extraction of Zn2+ using butanol from various chloride ion concentrations into 1- phenyl -3- methyl -4- trichloro acetyl pyrazolone -5 (HTcP) in benzene and hexane showed above 80% extraction yield. This was in contrast to 0% extraction of Zn2+ in the absence of butanol as a synergist throughout the pH range 0 - 7 studied. The data presented showed that extraction increases as chloride ion concentration increases from 0.1M to 1M. Also, overall optimal extraction is higher for extraction using (HTcP) in benzene than hexane while extraction of Zn2+ at lower pH value is more effective in hexane solution rather than benzene. Thus the presence of Cl- in buffer solution shows a salting out effect as the concentration in the buffer medium increases. Slope analysis showed that the extracted adduct complex specie had the formula Zn(TcP)2.2BuOH. The pH1/2, log Kex, log KD, the extraction mechanism and extracted species, for all the systems are presented. The relevant patents are discussed.

In the following review article we have given a brief overview about the synthesis, characterization and potential applications of various organically modified phosphate-based molecular sieves, metal-oxophenylphosphates and the patent literature of this field (since its discovery). These include the oxophenylphosphates of tin, titanium, niobium, iron, tantalum, calcium and zirconium. The characterization of the materials has been discussed in details, which includes nanostructure elucidation using powder X-ray diffraction, nitrogen adsorption/desorption, transmission and scanning electron microscopic studies, spectroscopic analysis using FT-IR, UV-Visible, 13C and 31P MAS NMR, XPS, and thermal analysis. These materials find potential applications in adsorption, shape-selective acid-base catalysis and can be used as membrane, support for anode and cathode material in fuel cell. The sulfonated materials derived from these hybrids show high Bronsted acidity, proton conductivity and selectivity for a number of acid catalyzed organic transformations.

This review is about the Argentina Patent number AR 047617B1 published on August 12, 2008. Its inventors are Gaggino Rosana, Arguello Ricardo and Berretta Horacio. The topic is a procedure to make new constructive elements (bricks and plates) by using these recycled plastics: - Low-density polyethylene (LDPE), recycled out of discarded soft drink packs. - Polyethylene-terephthalate (PET), recycled out of discarded soft drink bottles. - Several plastics, from the printed films used, like packages of candies (remainder of production plant by faults of inked or thickness). These conveniently grounded plastics were taken as aggregates to be mixed with Normal Portland cement, replacing heavy sand and gravel habitually used in these mixtures. These materials can be used in constructive elements such as bricks and plates for economic houses closures or traditional construction. The developed constructive elements offer high thermal insulation, so they can be used in closures with a smaller thickness than conventional bricks and blocks. Besides, they have a lower specific weight than these traditional constructive elements. Recycling means lowering costs, making part of the environment contaminating waste useful and providing the unemployed and/or unqualified work force with jobs through uncomplicated technologies. Therefore, it has an economical as well as ecological and socially concerned proposal.

Metallic electrodes have received great attention for the last thirty years due to their special characteristics and low price. Some properties such as adhesive properties and reliability remained uncertain. There are numerous published reports and patents in the literature which have been dedicated to thin metallic films. However, it has been seen that these reports most likely do not practicable. The goal of this study is to elucidate the restriction toward manufacturer and engineers to employ thin metallic films in microelectronic technology. Main disadvantages of the metallic thin films are classified into three major categories called adhesive properties, interdiffusion and solid state reactions, and hillock formation. Numerous inventions have been proposed to: enhance the adhesive properties of metallic films; suppress the solid state reactions within metallic films which occur at high temperature; and prevent the hillock formation. Applicable inventions are considered and new theories and suppressing procedures are described deeply in this review. This study not only represents the methods and inventions which are able to solve the mentioned problems, but also explains the scientific origin of each method, individually. The other advantage of this work is to introduce the recent progresses on alloy thin films as a potential replacement for metallic thin films.

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