Effect of carbon coating on mechanical strength of SiC whisker-reinforced alumina composites

1993 ◽  
Vol 19 (1) ◽  
pp. 61-67
Author(s):  
I. Thompson ◽  
V.D. Krstic
Keyword(s):  
Mechanical Strength ◽  
Carbon Coating ◽  
Alumina Composites

scholarly journals Classification and Properties of Dental Zirconia as Implant Fixtures and Superstructures

Materials ◽  
2021 ◽  
Vol 14 (17) ◽  
pp. 4879
Author(s):  
Seiji Ban
Keyword(s):  
Mechanical Strength ◽  
Bacterial Adhesion ◽  
Contact Region ◽  
Dental Materials ◽  
Occlusal Contact ◽  
Suitable Material ◽  
Yttria Content ◽  
Occlusal Wear ◽  
Alumina Composites ◽  
Oral Condition

Various types of zirconia are widely used for the fabrication of dental implant superstructures and fixtures. Zirconia–alumina composites, such as ATZ and NanoZR, are adequate for implant fixtures because they have excellent mechanical strength in spite of insufficient esthetic properties. On the other hand, yttria-stabilized zirconia has been used for implant superstructures because of sufficient esthetic properties. They are classified to 12 types with yttria content, monochromatic/polychromatic, uniform/hybrid composition, and monolayer/multilayer. Zirconia with a higher yttria content has higher translucency and lower mechanical strength. Fracture strength of superstructures strongly depends on the strength on the occlusal contact region. It suggests that adequate zirconia should be selected as the superstructure crown, depending on whether strength or esthetics is prioritized. Low temperature degradation of zirconia decreases with yttria content, but even 3Y zirconia has a sufficient durability in oral condition. Although zirconia is the hardest dental materials, zirconia restorative rarely subjects the antagonist teeth to occlusal wear when it is mirror polished. Furthermore, zirconia has less bacterial adhesion and better soft tissue adhesion when it is mirror polished. This indicates that zirconia has advantageous for implant superstructures. As implant fixtures, zirconia is required for surface modification to obtain osseointegration to bone. Various surface treatments, such as roughening, surface activation, and coating, has been developed and improved. It is concluded that an adequately selected zirconia is a suitable material as implant superstructures and fixtures because of mechanically, esthetically, and biologically excellent properties.

Mechanical and thermal properties of high-density polyethylene/alumina/glass fiber hybrid composites

2018 ◽  
Vol 32 (11) ◽  
pp. 1566-1581 ◽  
Author(s):  
Sergio Augusto B Lins ◽  
Marisa Cristina G Rocha ◽  
José Roberto M d’Almeida
Keyword(s):  
Thermal Stability ◽  
Thermal Properties ◽  
Elastic Modulus ◽  
Mechanical Strength ◽  
Glass Fiber ◽  
High Density Polyethylene ◽  
Hybrid Composites ◽  
Glass Fibers ◽  
Neat Polymer ◽  
Alumina Composites

In this investigation, composite materials made from high-density polyethylene (HDPE) and alumina, as well as from HDPE, alumina, and glass fibers, were prepared, aiming to improve the thermal stability, stiffness, and mechanical strength. The combined effects of alumina and glass fibers and the individual effects of alumina were studied. Alumina concentrations ranged from 5 wt% to 10 wt% and glass fiber concentrations ranged from 10 wt% to 30 wt%. For the hybrid composite materials, alumina concentration was maintained constant as the glass fiber concentration increased. The composites were processed with a double-screw extruder. Their properties were evaluated through a multi-analytical approach. Results pointed to a significant increase of the elastic modulus for the hybrid composite (up to 501% in comparison to the neat polymer), at the cost of a large decrease in toughness, alongside a decline in impact resistance. Elastic modulus improvement was observed in both hybrid and HDPE-alumina composites, being higher for the hybrid composites due to the addition of glass fibers. HDPE-alumina composites presented a decrease in mechanical strength, whereas the hybrid composites showed an increase of this parameter. Concerning thermal properties, the hybrid composites presented higher thermal stability than that of the HDPE-alumina composites and a similar degradation temperature as the neat polymer. Micrographs pointed to weak adhesion between alumina particles and the polymeric matrix as well as a slight degree of fiber detachment. Overall, the hybrid composites presented considerably higher stiffness and mechanical strength than the neat polymer and HDPE-alumina composite (19–26% increase), with no significant change in thermal stability.

Ca-Histochemistry in slime mold plasmodia

1978 ◽  
Vol 36 (2) ◽  
pp. 130-131
Author(s):  
Ulrich Dierkes
Keyword(s):  
Physarum Polycephalum ◽  
Carbon Coating ◽  
Freeze Drying ◽  
Freeze Fracture ◽  
Freeze Substitution ◽  
Uranyl Acetate ◽  
Slime Mold ◽  
Staining Procedure ◽  
Protoplasmic Streaming ◽  
Intracellular Ca

Calcium is supposed to play an important role in the control of protoplasmic streaming in slime mold plasmodia. The motive force for protoplasmic streaming is generated by the interaction of actin and myosin. This contraction is supposed to be controlled by intracellular Ca-fluxes similar to the triggering system in skeleton muscle. The histochemical localisation of calcium however is problematic because of the possible diffusion artifacts especially in aquous media.To evaluate this problem calcium localisation was studied in small pieces of shock frozen (liquid propane at -189°C) plasmodial strands of Physarum polycephalum, which were further processed with 3 different methods: 1) freeze substitution in ethanol at -75°C, staining in 100% ethanol with 1% uranyl acetate, and embedding in styrene-methacrylate. For comparison the staining procedure was omitted in some preparations. 2)Freeze drying at about -95°C, followed by immersion with 100% ethanol containing 1% uranyl acetate, and embedding. 3) Freeze fracture, carbon coating and SEM investigation at temperatures below -100° C.

Surface Structure in Microtomed Sections Caused by Glass and Diamond Knives

1971 ◽  
Vol 29 ◽  
pp. 456-457
Author(s):  
J. Temple Black ◽  
William G. Boldosser
Keyword(s):  
Plastic Deformation ◽  
Epoxy Resin ◽  
Carbon Coating ◽  
Surface Damage ◽  
Body Angle ◽  
Normal Manner ◽  
Bottom Side ◽  
Cutting Direction ◽  
Made In ◽  
Diamond Knife

Ultramicrotomy produces plastic deformation in the surfaces of microtomed TEM specimens which can not generally be observed unless special preparations are made. In this study, a typical biological composite of tissue (infundibular thoracic attachment) infiltrated in the normal manner with an embedding epoxy resin (Epon 812 in a 60/40 mixture) was microtomed with glass and diamond knives, both with 45 degree body angle. Sectioning was done in Portor Blum Mt-2 and Mt-1 microtomes. Sections were collected on formvar coated grids so that both the top side and the bottom side of the sections could be examined. Sections were then placed in a vacuum evaporator and self-shadowed with carbon. Some were chromium shadowed at a 30 degree angle. The sections were then examined in a Phillips 300 TEM at 60kv.Carbon coating (C) or carbon coating with chrom shadowing (C-Ch) makes in effect, single stage replicas of the surfaces of the sections and thus allows the damage in the surfaces to be observable in the TEM. Figure 1 (see key to figures) shows the bottom side of a diamond knife section, carbon self-shadowed and chrom shadowed perpendicular to the cutting direction. Very fine knife marks and surface damage can be observed.

Specimen Preparation for Clinical Applications of X-Ray Microanalysis

1990 ◽  
Vol 48 (2) ◽  
pp. 328-329
Author(s):  
J.D. Shelburne ◽  
G.M. Roomans
Keyword(s):  
Carbon Coating ◽  
Clinical Applications ◽  
Point Of View ◽  
Practical Significance ◽  
Sweat Test ◽  
Specimen Preparation ◽  
Tissue Preparation ◽  
X Ray ◽  
Gallbladder Stones ◽  
Clinical Problems

Proper preparative procedures are a prerequisite for the validity of the results of x-ray microanalysis of biological tissue. Clinical applications of x-ray microanalysis are often concerned with diagnostic problems and the results may have profound practical significance for the patient. From this point of view it is especially important that specimen preparation for clinical applications is carried out correctly.Some clinical problems require very little tissue preparation. Hair, nails, and kidney and gallbladder stones may be examined and analyzed after carbon coating. High levels of zinc or copper in hair may be indicative of dermatological or systemic diseases. Nail clippings may be analyzed (as an alternative to the more conventional sweat test) to confirm a diagnosis of cystic fibrosis. X-ray microanalysis in combination with scanning electron microscopy has been shown to be the most reliable method for the identification of the components of kidney or gallbladder stones.A quantitatively very important clinical application of x-ray microanalysis is the identification and quantification of asbestos and other exogenous particles in lung.

Assessment of Amorphous Carbon Coating for Artificial Joints Application

2005 ◽  
Vol 48 (2) ◽  
pp. 190-198 ◽  
Author(s):  
O. O. Ajayi ◽  
B. Shi ◽  
M. J. Soppet ◽  
A. Erdemir ◽  
H. Liang ◽  
...  
Keyword(s):  
Amorphous Carbon ◽  
Carbon Coating ◽  
Artificial Joints

FORMULATION AND DEVELOPMENT OF FAST DISSOLVING TABLET OF METOCLOPRAMIDE: AN ANTI-EMETIC DRUG

2019 ◽  
Vol 8 (6) ◽  
Author(s):  
Avilash Carpenter ◽  
M.K. Gupta ◽  
Neetesh Kumar Jain ◽  
Urvashi Sharma ◽  
Rahul Sisodiya
Keyword(s):  
Mechanical Strength ◽  
Standard Procedure ◽  
Flow Property ◽  
Storage Conditions ◽  
Angle Of Repose ◽  
Dissolution Time ◽  
Disintegration Time ◽  
Powder Blend ◽  
Standard Curve ◽  
The Stability

Aim: The main of the study is to formulate and develop orally disintegrating fast dissolving tablet of Metoclopramide hydrochloride. Material & Methods: Before formulation and development of selected drug, the standard curve in buffer was prepared and absorbance at selected maxima was taken. Then two different disintegrating agents were selected and drug was mixed with disintegrating agents in different ratio. Various Preformulation parameters and evaluation of tablet i.e. disintegration time, dissolution time, friability, hardness, thickness were measured by standard procedure. Result & Discussion: The angle of repose for all the batches prepared. The values were found to be in the range of 30.46 to 36.45, which indicates good flow property for the powder blend according to the USP. The bulk density and tapped density for all the batches varied from 0.49 to 0.54 g/mL and 0.66 to 0.73, respectively. Carr’s index values were found to be in the range of 23.33 to 25.88, which is satisfactory for the powders as well as implies that the blends have good compressibility. Hausner ratio values obtained were in the range of 1.22 to 1.36, which shows a passable flow property for the powder blend based on the USP. The results for tablet thickness and height for all batches was found to range from 4.45 to 4.72 mm and 3.67 to 3.69 mm, respectively. Hardness or breaking force of tablets for all batches was found to range from 32.8 to 36.2 N. Tablet formulations must show good mechanical strength with sufficient hardness in order to handle shipping and transportation. Friability values for all the formulations were found to be in the range of 0.22 % to 0.30 %. Conclusion: Orally disintegrating tablets were compressed in order to have sufficient mechanical strength and integrity to withstand handling, shipping and transportation. The formulation was shown to have a rapid disintegration time that complied with the USP (less than one minute). The data obtained from the stability studies indicated that the orally disintegrating mini-tablets of MTH were stable under different environmental storage conditions. Keywords: Formulation & Development, Fast Dissolving Tablet, Metoclopramide, Anti-Emetic Drug, Oral Disintegrating Tablet

Plasma Enhanced Chemical Vapor Deposition of Porous Organosilicate Glass ILD Films With k ≤ 2.4.

2003 ◽  
Vol 766 ◽  
Author(s):  
Raymond N. Vrtis ◽  
Mark L. O'Neill ◽  
Jean L. Vincent ◽  
Aaron S. Lukas ◽  
Brian K. Peterson ◽  
...  
Keyword(s):  
Dielectric Constant ◽  
Chemical Vapor Deposition ◽  
Mechanical Strength ◽  
Thermal Annealing ◽  
Vapor Deposition ◽  
Chemical Vapor ◽  
Organosilicate Glass

AbstractWe report on our work to develop a process for depositing nanoporous organosilicate (OSG) films via plasma enhanced chemical vapor deposition (PECVD). This approach entails codepositing an OSG material with a plasma polymerizable hydrocarbon, followed by thermal annealing of the material to remove the porogen, leaving an OSG matrix with nano-sized voids. The dielectric constant of the final film is controlled by varying the ratio of porogen precursor to OSG precursor in the delivery gas. Because of the need to maintain the mechanical strength of the final material, diethoxymethylsilane (DEMS) is utilized as the OSG precursor. Utilizing this route we are able to deposit films with a dielectric constant of 2.55 to 2.20 and hardness of 0.7 to 0.3 GPa, respectively.

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