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Hardness Values (hardness + value)
Selected AbstractsTribology,Structure Relationships in Silicon Oxycarbide Thin FilmsINTERNATIONAL JOURNAL OF APPLIED CERAMIC TECHNOLOGY, Issue 5 2010Joseph V. Ryan Silicon oxycarbide is a versatile material system that is attractive for many applications because of its ability to tune properties such as chemical compatibility, refractive index, electrical conductivity, and optical band gap through changes in composition. One particularly intriguing application lies in the production of biocompatible coatings with good mechanical properties. In this paper, we report on the wide range of mechanical and tribological property values exhibited by silicon oxycarbide thin films deposited by reactive radio frequency magnetron sputtering. Through a change in oxygen partial pressure in the sputtering plasma, the composition of the films was controlled to produce relatively pure SiO2, carbon-doped SiC, and compositions between these limits. Hardness values were 8,20 GPa over this range and the elastic modulus was measured to be between 60 and 220 GPa. We call attention to the fit of the mechanical data to a simple additive bond-mixture model for property prediction. Tribological parameters were measured using a ball-on-disk apparatus and the samples exhibited the same general trends for friction coefficient and wear rate. One film is shown to produce variable low friction behavior and low wear rate, which suggests a solid-state self-lubrication process because of heterogeneity on the nanometer scale. [source] EFFECT OF CaCl2 AND CONVECTIVE-OSMOTIC DRYING ON TEXTURE AND PREFERENCE OF APPLEJOURNAL OF FOOD QUALITY, Issue 6 2006L.A. OCHOA-MARTÍNEZ ABSTRACT Conventional air-drying combined with osmotic dehydration was researched as a potential method for drying apple cubes of superior quality. Samples were pretreated with CaCl2 at different temperatures and times. Pretreated apple cubes were dehydrated in a tray dryer. Then, osmotic dehydration with sucrose solutions was carried out. The curves for osmotic dehydration showed that the gain of solids was higher when 40% of water was removed by convective drying while the loss of weight was lower at the same level of dehydration at 65°Brix. Texture measurements indicated that the temperature of pretreatment affected the hardness and cohesiveness. Hardness values were higher at 40C, while cohesiveness values were lower at the same temperature. The CaCl2 at a given temperature did not have a significant effect on texture. Sensory evaluation showed that samples pretreated at 25C and osmotically dried at 50°Brix had the higher preference by the judges. [source] Spark Plasma Sintering of AluminaJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 8 2002Zhijian Shen A systematic study of various spark plasma sintering (SPS) parameters, namely temperature, holding time, heating rate, pressure, and pulse sequence, was conducted to investigate their effect on the densification, grain-growth kinetics, hardness, and fracture toughness of a commercially available submicrometer-sized Al2O3 powder. The obtained experimental data clearly show that the SPS process enhances both densification and grain growth. Thus, Al2O3 could be fully densified at a much lower temperature (1150°C), within a much shorter time (minutes), than in more conventional sintering processes. It is suggested that the densification is enhanced in the initial part of the sintering cycle by a local spark-discharge process in the vicinity of contacting particles, and that both grain-boundary diffusion and grain-boundary migration are enhanced by the electrical field originating from the pulsed direct current used for heating the sample. Both the diffusion and the migration that promote the grain growth were found to be strongly dependent on temperature, implying that it is possible to retain the original fine-grained structure in fully densified bodies by avoiding a too high sintering temperature. Hardness values in the range 21,22 GPa and fracture toughness values of 3.5 ± 0.5 MPa·m1/2 were found for the compacts containing submicrometer-sized Al2O3 grains. [source] A new technique for non-destructive field measurement of rock-surface strength: an application of the Equotip hardness tester to weathering studiesEARTH SURFACE PROCESSES AND LANDFORMS, Issue 12 2007Hisashi Aoki Abstract Tafone-like depressions have developed on the Aoshima sandstone blocks used for a masonry bridge pier in the coastal spray zone. A thin layer of partial granular disintegration was found on the surface in depressions. To evaluate quantitatively the strength of the thin weathered layer, the hardness was measured at the surface of the sandstone blocks using both an Equotip hardness tester and an L-type Schmidt hammer. Comparison of the two testing results indicates that the Equotip hardness value is more sensitive in evaluating the strength of a thin layer of weathered surface rock than the Schmidt hardness value. By applying two methods, i.e. both the repeated impact method and the single impact method, the Equotip tester can evaluate the strengths of fresh internal and weathered surficial portions of rocks having a thin weathering layer. Comparison of the two strengths enables evaluation of strength reduction due to weathering. Copyright © 2007 John Wiley & Sons, Ltd. [source] Human enamel dissolution in citric acid as a function of pH in the range 2.30,pH,6.30 , a nanoindentation studyEUROPEAN JOURNAL OF ORAL SCIENCES, Issue 3 2003Michele E. Barbour The objective of this study was to investigate the dissolution of human enamel in citric acid solutions over a wide range of pH. The in vitro conditions are considered to be relevant to soft drink-induced enamel erosion. Nanoindentation was used to investigate changes in the nanomechanical properties of polished enamel surfaces after exposure to citric acid solutions. Solutions used had 38.1 mmol l,1 citric acid and pH greater than 2.3 but less than 6.3 (2.30 pH 6.30). Samples were exposed to rapidly stirred, constant composition solutions for 120 s. Statistically significant changes in enamel hardness and reduced elastic modulus were observed after exposure to all solutions. There was an approximately linear dependence of enamel hardness on solution pH for 2.90 pH 6.30. Below pH 2.90, enamel is thought to have reached the lowest possible hardness value. The reduction in enamel dissolution caused by an increase in pH of a soft drink is likely to be small. Product modification to reduce the erosive potential of drinks may require additional methods such as addition of calcium salts. [source] Nanocomposite Hard Coatings: Deposition Issues and Validation of their Mechanical Properties,ADVANCED ENGINEERING MATERIALS, Issue 5 2005P. Schwaller Abstract The limitations of conventional coatings due to inferior hardness or poor oxidation stability can be overcome by nanocomposite hard coatings such as nc-TiN/a-SiNx, which consists of nanocrystalline TiN and a non-crystalline tissue phase of SiNx which are mutually immiscible. The properties of nanocomposite coatings, especially their increased hardness, can be explained by their nanostructure, which leads to a maximum hardness at typically 80 atomic percent of the crystalline phase. We show that enhanced hardness can only be attained when the silicon nitride phase is sufficiently nitrided. The accurate and reliable measurement of the hardness and elastic modulus requires the use of appropriate nanoindentation equipment and a careful tip correction with periodical validation. It is shown that for a correct hardness determination of a few microns thick nanocomposite coatings, an indentation depth of 100,nm is sufficient. The maximum hardness of our nc-TiN/a-SiNx coatings deposited by a hybrid UBM/arc-PVD process is about 40,GPa. This value represents a global hardness value, due to the nanocomposite structure there may be a local hardness variation of about ±10,%. [source] Composition, soaking, cooking properties and thermal characteristics of starch of chickpeas, wrinkled peas and smooth peasINTERNATIONAL JOURNAL OF FOOD SCIENCE & TECHNOLOGY, Issue 5 2001Beata Klamczynska We investigated both the distribution of protein, ash and starch in legume (chickpeas, smooth and wrinkled peas) cotyledons, and the soaking and cooking characteristics, including gelatinization and retrogradation, of the starch. There were large differences in composition between different types of legumes and also between the outer and inner parts of legume cotyledons. Wrinkled peas exhibited much higher water absorption during prolonged soaking and there were higher hardness value determined for cooked seeds compared with chickpeas and smooth peas. While the hardness of cooked seeds decreased continuously as cooking time increased to 110 min, all legume starch was fully gelatinized after cooking for 70 min. [source] Carotenoid Content and Physicochemical and Sensory Characteristics of Carrot Chips Deep-Fried in Different Oils at Several TemperaturesJOURNAL OF FOOD SCIENCE, Issue 9 2001A. Sulaeman ABSTRACT: The influence of deep-frying using different oils and temperatures on carotenoid content and physicochemical and sensory characteristics of carrot chips was investigated. Sliced carrots were steam-blanched, cooled, soaked in 0.2% sodium metabisulfite, and deep-fried in canola, palm, or partially hydrogenated soybean oil (PHSO) at 165, 175, or 185 °C. Frying temperature, but not oil, significantly (P < 0.05) affected the ,-carotene, ,-carotene, and total carotenoid contents. Oil type significantly (P < 0.05) influenced all color values. Increasing temperature lowered the redness value, which correlated with decreased carotenoid content, color darkening, and decreased hardness value. Trained panelists detected no differences among oil types in crispness, sweetness, odor, and acceptability. The best carrot-chip product was that fried in PHSO at 165 °C. [source] Production of B4C coatings by CVD method in a dual impinging-jet reactor: Chemical yield, morphology, and hardness analysisAICHE JOURNAL, Issue 11 2009Mustafa Karaman Abstract ,-rhombohedral boron carbide (B4C) was deposited on a tungsten substrate from a BCl3H2CH4 gas mixture in a dual impinging-jet chemical vapor deposition reactor. On-line FTIR analysis of the product stream proved the formation of BHCl2 and HCl as by products, in a competing parallel reaction. A maximum of 13% chemical yield of boron carbide was observed, and the yield was found to have increasing trend with an increase in temperature. XRD analysis proved the existence of rhombohedral B4C phase at 1300°C without any other B4C phases or impurities. At this temperature, the formation of 5-fold icosahedral boron carbide crystals up to 30 micron sizes was observed. Such highly symmetric crystalline regions were observed to have a very high hardness value of 4750 kg/mm2 as revealed from the microhardness analysis. The change in product morphology at low substrate temperatures resulted in a decrease in the hardness values. © 2009 American Institute of Chemical Engineers AIChE J, 2009 [source] About 200 years after Mohs , Nanoscratching LiB3O5CRYSTAL RESEARCH AND TECHNOLOGY, Issue 11 2008P. Paufler Abstract Though simple scratch hardness tests after Mohs are still used today, the development of diamond nanoscratching equipment offers new possibilities to meet demands of modern nanotechnology. Preceding approaches to assign hardness values to materials are briefly reviewed, and scratch hardness is related to indentation hardness. Taking single-crystalline LiB3O5 as an example, the dependence of scratch morphology on the direction of scratching is demonstrated quantitatively. The coefficient of friction depends on normal load and varies between 0.25 and 0.37. Moreover, it is oscillating during scratching thus reflecting processes at nanoscale. Dislocation etch pits were observed due to scratching. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Influence of water quality and age on nickel toxicity to fathead minnows (Pimephales promelas)ENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 1 2004Tham Chung Hoang Abstract This research characterized the effects of water quality and organism age on the toxicity of nickel (Ni)to fathead minnows (Pimephales promelas) to facilitate the accurate development of site-specific water-quality criteria. Nickel sulfate hexa-hydrate (NiSO4·6H2O) was used as the Ni source for performing acute toxicity tests (median lethal concentration after 96-h exposure [96-h LC50]) with <1-d-old and 28-d-old P. promelas under varying regimes of hardness, pH, alkalinity, and natural organic matter (NOM). The toxicity of Ni was inversely related to water hardness between hardness values of 20 and 150 mg/L (as CaCO3). Below 30 mg/L alkalinity, Ni toxicity was related to alkalinity. The effect of pH was confounded by hardness and the presence of NOM. In the absence of NOM, the toxicity of Ni increased as pH increased at high hardness and alkalinity. In general, 28-d-old fish were less sensitive than <1-d-old fish to Ni. This lower sensitivity ranged from 12-fold at low hardness and alkalinity (20 and 4 mg/L, respectively) to 5-fold at high hardness and alkalinity (100 and 400 mg/L, respectively). The presence of NOM (10 mg/L as dissolved organic carbon [DOC]) reduced Ni toxicity by up to 50%, but this effect appeared to be saturated above DOC at 5 mg/L. Incubating Ni with the NOM solution from 1 to 17 days had no effect on Ni toxicity. When using multivariate analysis, the 96-h LC50 for Ni was a function offish age, alkalinity, hardness, and NOM (96-h LC50 = ,0.642 + 0.270(fish age) + 0.005(alkalinity) + 0.018(hardness) + 0.138(DOC)). When using this model, we found a strong relationship between measured and predicted 96-h LC50 values (r2 = 0.94) throughout the treatment water qualities. The biotic ligand model (BLM) did not accurately predict Ni toxicity at high or low levels of alkalinity. Results of our research suggest that the BLM could be improved by considering NiCO3 to be bioavailable. [source] PE-UHMW in Hip Implants: Properties of Conventional and Crosslinked Prosthetic ComponentsADVANCED ENGINEERING MATERIALS, Issue 10 2009Ruth Markut-Kohl Hip implants made of crosslinked ultra high molecular weight polyethylene,PE-UHMW,(different as-received conditions) are compared with a retrieval made from non-crosslinked PE-UHMW and a control PE-UHMW. Oxidation leads to recrystallization and the enhanced crystallinity corresponds to higher hardness values. These structure-property relations are discussed for conventional PE-UHMW and also for crosslinked material. [source] Influence of Wet Mechanical Mixing on Microstructure and Vickers Hardness of Nanocrystalline Ceramic,Metal CompositesINTERNATIONAL JOURNAL OF APPLIED CERAMIC TECHNOLOGY, Issue 5 2008Tatsuo Kumagai Nanocrystalline (nc) ceramic,metal composite bulk samples have been fabricated by consolidation of mixture of attrition-milled (AM) amorphous base ceramic ((ZrO2,3 mol% Y2O3),20 mol% Al2O3) and AM amorphous base metallic (Ti,48 mol% Al) powders using a pulse-current pressure sintering system. Microstructural observations revealed that the ceramic and metallic colonies appear blocky in morphology in the composite bulk samples, and both the ceramic and the metallic colonies consist of a large number of equiaxed fine grains with the sizes of 78,82 and 81,86 nm, respectively. Mechanical mixing treatments by wet ball milling in ethanol before consolidation process are effective for refinement of the ceramic and metallic colonies. In all the obtained composite bulk samples, the ceramic colonies consist of the dominant phase of tetragonal (t) ZrO2 solid solution (ss) together with the minor phases of monoclinic (m) ZrO2ss and ,-Al2O3. On the other hand, the dominant phase in the metallic colonies changes from Ti3Al (,2) to Tiss (,) with an increase in the t -ZrO2ss volume fraction by abrasion of 3 mol% yttria-stabilized tetragonal polycrystalline zirconia balls during wet mechanical mixing treatments. Such a phase transformation from ,2 to , is considered to be due to the decrease in the aluminum content in the metallic colonies by combination of aluminum with oxygen (i.e., the formation of ,-Al2O3), which is probably taken from ethanol (C2H5OH) into the powders during wet mechanical mixing treatments. The obtained nc composite bulk samples show good Vickers hardness values, which are considerably higher than those estimated from the rule of mixture. [source] Properties of nanocomposites based on maleate-vinyl ether donor,acceptor UV-curable systemsJOURNAL OF APPLIED POLYMER SCIENCE, Issue 6 2007Neena Ravindran Abstract UV-curable nanocomposites based on donor,acceptor crosslinking chemistry were prepared containing organically modified montmorillonites. The coatings were characterized for thermal, mechanical, and morphological properties. X-ray diffraction and transmission electron microscopy showed that nanocomposites were formed in all samples. Results showed that an increase in the percentage of clay caused an increased modulus and glass-transition temperature. It was also seen that tensile modulus showed dramatic improvement when compared with the unmodified polyester sample. Real time IR kinetic data showed that higher conversions were obtained at higher clay loadings. Pendulum hardness values and tensile modulus values showed different trends in properties depending on the combination of polymer matrix and organomodification. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007 [source] On the applicability of the HSAB principle through the use of improved computational schemes for chemical hardness evaluationJOURNAL OF COMPUTATIONAL CHEMISTRY, Issue 7 2004Mihai V. Putz Abstract Finite difference schemes, named Compact Finite Difference Schemes with Spectral-like Resolution, have been used for a less crude approximation of the analytical hardness definition as the second-order derivative of the energy with respect to the electron number. The improved computational schemes, at different levels of theory, have been used to calculate global hardness values of some probe bases, traditionally classified as hard and soft on the basis of their chemical behavior, and to investigate the quantitative applicability of the HSAB principle. Exchange acid-base reactions have been used to test the HSAB principle assuming the reaction energies as a measure of the stabilization of product adducts. © 2004 Wiley Periodicals, Inc. J Comput Chem 25: 994,1003, 2004 [source] INFLUENCE OF SODIUM TRIPOLYPHOSPHATE (STP) TREATMENT AND COOKING TIME ON COOK LOSSES AND TEXTURAL PROPERTIES OF RED MEATSJOURNAL OF FOOD PROCESS ENGINEERING, Issue 6 2007S. BELGIN ERDOGDU ABSTRACT Sodium tripolyphosphates (STPs) are important functional additives used in meat products. STPs reduce cook losses and improve textural properties, especially by increasing the water-holding capacity of proteins. However, increases in cooking time or temperature enhance meat proteins' denaturation, resulting in a reduced water-holding capacity. The amount of STPs diffused into meats would play an important role for these changes. Therefore, the objectives of this research were to determine the effects of processing conditions (cooking time, STP concentration and dipping time) on cook losses and textural properties of red meats, and to relate these changes with diffused amount of STPs. For this purpose, meats (2 × 2 × 2 cm in size) were dipped in different concentrations of STP solutions (2, 4 and 6%) for 10, 20 and 30 min, and were cooked in boiling water for 5, 10 and 15 min. Cook losses were calculated from weight changes, and textural properties were determined by applying texture profile analysis to data obtained using Texture Analyzer TA-XT2i (Stable Micro Systems, Godalming, Surrey, U.K.). STPs were found to decrease cook losses and hardness values. While an increase in STP concentration increased cohesiveness, increase in cooking time resulted in higher hardness, gumminess, chewiness and cook losses. An increase in dipping times also decreased the cook losses and hardness. The results showed that STP concentration, STP dipping and cooking times had significant effects on the changes of textural properties and cook losses of meats. These results may be used for further meat processing optimization studies if they get correlated with sensory data obtained at the same conditions. PRACTICAL APPLICATIONS Cooking to assure safety of food products leads to changes in sensory attributes. The major changes occurring in meats are shrinkage, toughening of tissues, releasing of meat juice and color due to the effect of thermal treatment on proteins. Based on these, resulting cook losses for economical considerations and changes in textural properties affecting consumer satisfaction are widely recognized. Because the meat processing industry uses sodium tripolyphosphates (STPs) to improve textural properties and to reduce cook losses, the objective of this research was to determine the effects of STPs and cooking time on cook losses and textural properties of red meats. The results showed that STPs and cooking time affected the changes in cook losses and textural properties significantly. In addition to these results, an optimization study for decreasing cook losses while improving textural properties should be conducted where these changes are attributed to be significant for human perception using a sensory panel. [source] Automatic regulation of occlusal force because of hardness-change of the bite objectJOURNAL OF ORAL REHABILITATION, Issue 1 2008A. SHIMADA Summary, It is considered that the information of chewed food, such as size and texture, is important for smooth mastication. In this study, we analysed aspects of the control of occlusal force, by experimentally reproducing situations in which the hardness of food changed unpredictably during mastication, using a device that utilized a 3-sectioned urethane rubber piece with different hardness values. Seven healthy subjects were instructed to perform repetitive jaw open,close movements paced by a metronome (1·0 Hz) and to maintain constant occlusal force throughout the trial. Using the device, the following parameters were measured during the first to fifth strokes after changing the hardness, peak value, impulse, duration and time to peak of occlusal force in the waveform of occlusal force, cycle time of open,close jaw movements, jaw gape and maximum speed in the closing phase in the waveform of the jaw movements. Each parameter value was statistically analysed by anova with Fisher's least significant difference method (P < 0·05). Peak occlusal force, impulse and jaw gape were significantly affected by the change in hardness, while an increase in hardness caused increases in the values for peak occlusal force and impulse against the instruction, after which those values remained constant while the subjects occluded the same level of hardness. Our results indicate that the level of the resulting occlusal force is regulated automatically according to the hardness of the chewed food. We concluded that occlusal force was adapted for efficient mastication when the hardness of foods changes unpredictably. [source] | ||||||||||||||||