Characterization of Surface-Modified Halloysite Nanotubes by Thermal Treatment Under Reducing Atmosphere.

In recent years, the halloysite (Al₂Si₂O(OH)₄ · 2H₂O) has been highlighted owing to its naturally occurring one-dimensionalmicrostructure that enables versatile applications. Due to the demand for enhancing surface interaction, several types of research such as acid/base treatments have been conducted on the halloysite nanotubes. The objective of this study is to investigate the structural and surface properties of thermally treated halloysites under reducing atmosphere.

Separation of Halloysite Nano Tubes (HNTs) by Homogenization of Quartz Contaminated Kaolins.

Natural halloysite kaolin contains a lot of impurities such as quartz phases and varies in morphology and size during their formation in the earth. So to utilize as a new type of natural nano material, removing quartz impurities from kaolin clays without scathe the tube morphologies are necessary. So to remove quartz impurities from kaolin by forming a well deflocculated aqueous slip without fracturing the morphology of tubes, the slip of homogenized halloysite clay was recovered by adding polyvalent metallic cations and anionic polyelectrolyte flocculants simultaneously to selectively flocculate the mixture of quartz and halloysite, whereby the halloysite particles form floes and the tubular halloysite remains in suspensions.

Interfacial Property of Dental Cobalt–Chromium Alloys and Their Bonding Strength with Porcelains.

Porcelain-fused-to-metal crown is one of the widely-used prostheses among the dental porcelain restorations. Nonprecious metals like Ni–Cr and Co–Cr have extensively been used for metal-ceramic restorations due to advantages such as inexpensive price, hardness, durability, resistance to deformation, thin thickness of metal of porcelain area, and other mechanical and physical properties. However, the immediate advantage of the Co–Cr alloy is comparable performance to other base metal alloys, but without an allergenic nickel component.

Polylactic Acid/Nanostructured Si-Substituted -Tricalcium Phosphate Composites for Biodegradable Fixation Medical Devices.

Organic/inorganic biocomposite materials for biodegradable fixation medical devices require osteoconductivity, biocompatibility, and adequate mechanical properties with biodegradation behavior. The objective of this study was to investigate the effect of Si ions substituted in β-tricalcium phosphate (β-TCP) on the mechanical properties of organic/inorganic biocomposites. Biodegradable composite materials were prepared with polylactic acid (PLA) as the matrix and nano Si-substituted β-TCP as the osteoconductive filler by solvent mixing and conventional molding.

Fabrication of Wollastonite Coatings on Zirconia by Room Temperature Spray Process.

Wollastonite-based bioceramic powders were synthesized by solid-state reaction between calcite and silica powder. To control the phase and bioactivity of wollastonite, we also prepared four kinds of wollastonite-based bioceramics by adding an enstatite (MgSiO3) powder. After solid state reaction at 1000-1300 degrees C, micron-sized powders were obtained by milling and screening.

Microscale tribological behavior and in vitro biocompatibility of graphene nanoplatelet reinforced alumina.

Graphene nanoplatelets were added as reinforcement to alumina ceramics in order to enhance microscale tribological behavior, which would be beneficial for ceramic-on-ceramic hip implant applications. The reduction in microscale wear is critical to hip implant applications where small amounts of wear debris can be detrimental to patients and to implant performance. The addition of the GNPs lead to improvements in fracture toughness and wear (scratch) resistance of 21% and 39%, respectively.

Surface Corrosion of Nanoscaled Hydroxyapatite During an In Vivo Experiment.

Hydroxyapatite (HA) is widely used as a bioactive ceramics as it forms a chemical bond with bone. However, the drawback to using this material is its inferior mechanical properties. In this research, surface corrosion and disintegration of nanoscaled HA in a dog were studied, and the mechanism by which phase-pure HA dissolved in vivo was investigated.

Long and short range order structural analysis of In-situ formed biphasic calcium phosphates.

Background: Biphasic calcium phosphates (BCP) have attracted considerable attention as a bone graft substitute. In this study, BCP were prepared by aqueous co-precipitation and calcination method. The crystal phases of in-situ formed BCP consisting of hydroxyapatite (HAp) and β-tricalcium phosphate (β-TCP) were controlled by the degree of calcium deficiency of precursors.

Influence of Starting Powders on Hydroxyapatite Coatings Fabricated by Room Temperature Spraying Method.

Three types of raw materials were used for the fabrication of hydroxyapatite coatings by using the room temperature spraying method and their influence on the microstructure and in vitro characteristics were investigated. Starting hydroxyapatite powders for coatings on titanium substrate were prepared by a heat treatment at 1100 °C for 2 h of bovine bone, bone ash, and commercial hydroxyapatite powders. The phase compositions and Ca/P ratios of the three hydroxyapatite coatings were similar to those of the raw materials without decomposition or formation of a new phase.

Morphologies of nano-sized apatite formed on titanium substrate by biomimetic process.

The apatite was formed on the titanium plates with NaOH and heat treatments by biomimetic process. The influence of titanium surface microstructure on the apatite formation onto titanium substrate in SBF solution was investigated. After biomimetic process, nano-sized apatite layers were found on the Ti plates with NaOH and heat treatments.

Improvement of the stability of hydroxyapatite through glass ceramic reinforcement.

Hydroxyapatite has achieved significant application in orthopedic and dental implants due to its excellent biocompatibility. Sintered hydroxyapatites showed significant dissolution, however, after their immersion in water or simulated body fluid (SBF). This grain boundary dissolution, even in pure hydroxyapatites, resulted in grain separation at the surfaces, and finally, in fracture.

Nanostructured hydroxyapatite by microwave sintering.

In this work, nanostructured HA ceramics with dense microstructure were prepared by microwave sintering process and their microstructures were compared with the case of conventional sintering. Commercially obtained HA powder with Ca/P molar ratio of 1.67 was used as a starting material.