Greater Hardness Research Articles

Preparation and Evaluation of Taste Masked Orally Disintegrating Tablets with Granules Made by the Wet Granulation Method

Using furosemide (FU) as a model drug, we examined the wet granulation method as a way to improve the taste masking and physical characteristics of orally disintegrating tablets (ODTs). In the wet granulation method, yogurt powder (YO) was used as a corrective and maltitol (MA) was used as a binding agent. The taste masked FU tablets were prepared using the direct compression method. Microcrystalline cellulose (Avicel® PH-302) and mannitol were added as excipients at a mixing ratio of 1/1 by weight. Based on the results of sensory test on taste, the prepared granules markedly improved the taste of FU, and a sufficient masking effect was obtained at the YO/FU ratio of 1 or more. Furthermore, it was found that the masking effect achieved by YO granules made with the wet granulation method was similar to or better than that produced by the granules made with dry granulation method. All types of tablets displayed sufficient hardness (over 3.5×10(-2) kN), and rapidly disintegrating tablets were obtained with YO granules produced at a mixing ratio of FU/YO=1/1, which disintegrated within 20 s. Disintegration time lengthened as the mixing ratio of YO to FU increased. In the mixing ratio of FU/YO=1/1, the hardness of tablets with granules made by the wet granulation method exceeded that of tablets with granules made by the dry granulation method, with minimal differences in disintegration time. The hardness and disintegration time of the tablets with granules made by the wet granulation method could be controlled by varying the compression force. In conclusion, YO was found to be a useful additive for masking unpleasant tastes. FU ODTs with improved taste, rapid disintegration and greater hardness could be prepared with YO-containing granules made by the wet granulation method using MA as a binding agent.

Solid Particle Erosion-Wear Behavior of Alumina Ceramics at High-Temperature

In this paper, effects of temperature and erosion-wear particle on solid particle erosion-wear behavior of alumina ceramics were studied. The erosion-wear experiments were performed using self-designed sand blasting high-temperature solid particle erosion-wear equipment in air atmosphere. The results show that alumina ceramics presented the characteristics of brittle fracture at the high temperature of 1200°C. Erosion-wear rate increased with increasing temperature and rise obviously above 1000°C. For the same kind of erosion-wear particles, the erosion-wear rate of samples increased with the larger particle size. For the different ones, the greater hardness, the more serious erosion-wear.

Mechanical properties and microstructural analysis of an AgPd alloy cast under different temperatures

The metal restorations are used in Dentistry a long time ago. Nowadays we have resources that can get casting more accurate, with new material and equipments and techniques more precise. The purpose of this study was to evaluate the metallurgical and mechanical aspects of the AgPd dental alloy when it was submitted to different casting temperatures. It was used 30 specimens, divided in three groups (n=10): a) control group (no cast); b) casting temperature in accordance with the manufactures’ instructions (T1); b) casting temperature above manufactures´ instructions (like a torch) (T2). It was evaluated chemical and metallographic aspects, mechanical properties and Vickers hardness. The results showed a microstructure similar to T1 and T2 conditions, but with greater amount of light phase and particles in this last one. It was observed that the rupture tensile strength for the T1 condition was greater than the T2. The alloy in the no cast condition presented greater hardness but there was no statistically significant difference between T1 and T2. Supporting by the metallographic and mechanical results, it may predict that when elevated temperatures was used, above manufacture´s recommendations, it can occur failures in the prosthesis, like porosities, fissures or cracks.

Thermal and mechanical properties of sintered bodies and EB-PVD layers of Y 2O 3 added Gd 2Zr 2O 7 ceramics for thermal barrier coatings

In this study, the sintered bodies and EB-PVD coatings of gadolinium zirconate (Gd 2Zr 2O 7) ceramics with thermal and elastic resistance are prepared by the addition of yttrium oxide (Y 2O 3) to the composition of Gd 2Zr 2O 7 for thermal barrier coatings. XRD analysis reveals that the Y 2O 3-doped Gd 2Zr 2O 7 thermal barrier material has a thermally stable pyrochlore structure. The Y 2O 3-doped Gd 2Zr 2O 7 shows lower thermal conductivity than Y 2O 3-doped stabilized zirconia (YSZ), from 2.12 W/m K to 0.82–1.32 W/m K, and greater hardness than pure Gd 2Zr 2O 7, from 6 GPa to 10 GPa as measured by Vickers indentation and more than 20 GPa by nano-indentation, mainly owing to changes in the microstructure. The indentation stress–strain curves and load–penetration depth curves obtained by Hertzian and nano-indentation measurements indicate that the behavior of the curve is crucially influenced by the addition of Y 2O 3 to the pure Gd 2Zr 2O 7. The results suggest that Y 2O 3-doped Gd 2Zr 2O 7 may be expected to yield hardness and thermal insulation properties superior to those of commercial YSZ coatings for thermal barrier coatings on high temperature alloys.

Germination Conditions Affect Selected Quality of Composite Wheat‐Germinated Brown Rice Flour and Bread Formulations

Brown rice has been reported to be more nutritious after germination. Germinated brown rice flours (GBRFs) from different steeping conditions (in distilled water [DI, pH 6.8] or in a buffer solution [pH 3] for either 24 or 48 h at 35 degrees C) were evaluated in this study. GBRF obtained from brown rice steeped at pH 3 for 48 h contained the highest amount of free gamma aminobutyric acid (GABA; 67 mg/100 g flour). The composite flour (wheat-GBRF) at a ratio of 70 : 30 exhibited significantly lower peak viscosity (PV) (56.99 - 132.45 RVU) with higher alpha-amylase activity (SN = 696 - 1826) compared with those of wheat flour (control) (PV = 136.46 RVU and SN = 1976). Bread formulations, containing 30% GBRF, had lower loaf volume and greater hardness (P < 0.05) than the wheat bread. However, the hardness of bread containing 30% GBRF (except at pH 6.8 and 24 h) was significantly lower than that of bread containing 30% nongerminated brown rice flour (BRF). Acceptability scores for aroma, taste, and flavor of breads prepared with or without GBRFs (30% substitution) were not significantly different, with the mean score ranging from 6.1 (like slightly) to 7 (like moderately). Among the bread formulations containing GBRF, the one with GBRF prepared after 24 h steeping at pH 3 had a slightly higher (though not significant) overall liking score (6.8). This study demonstrated that it is feasible to substitute wheat flour with up to 30% GBRF in bread formulation without negatively affecting sensory acceptance. Practical Application: Our previous study revealed that flours from germinated brown rice have better nutritional properties, particularly gamma-aminobutyric acid (GABA), than the nongerminated one. This study demonstrated feasibility of incorporating up to 30% germinated brown rice flour in a wheat bread formulation without negatively affecting sensory acceptance. In the current United States market, this type of bread may be sold as frozen bread which would have a longer shelf life. Further study is thus needed.

A Simple Theoretical Method to Predict the Hardness of Pure Metal Crystals

Design of superhard bulk materials requires predicting their hardness, challenging current theories for material design. By introducing a concept of condensing force (CF), it is shown via ab initio calculations for fcc (Ni, Cu, Al, Ir, Rh, Au, Ag, Pd) and hcp Re crystals that materials with larger CF can have greater hardness. Since the calculation of CF is easy, this method might prove a convenient way to evaluate the hardness of newly designed materials.

Structure and Mechanical Properties of Diamond-Like Carbon Films Prepared from C2H2 and H2 Mixtures by Pulse Plasma Chemical Vapor Deposition

Diamond-like carbon (DLC) films were prepared by dc pulse plasma chemical vapor deposition (CVD). The hydrogen flow ratio [H2/(C2H2+H2)] was varied from 0 to 0.75, and the pulse frequency was varied from 1 to 20 kHz. Then, the relationship between film structure and hardness was investigated. At H2/(C2H2+H2)=0, films prepared at 10 kHz have the greatest hardness because a further increase in pulse frequency leads to an increase in the number of regular sixfold ring structures in the film and excessive ion peening on the growth face. The hardness at H2/(C2H2+H2)=0.5 is greater than that at H2/(C2H2+H2)=0 because the effect of ion peening and the number of regular sixfold ring structures at H2/(C2H2+H2)=0.5 are suitable for fabricating hard films. In contrast, at H2/(C2H2+H2)=0.75, the hardness is lower than that at H2/(C2H2+H2)=0 because of the reduced effect of ion peening; thus, the effect of an increase in the number of polymer bonds becomes significant.

A laboratory evaluation of the physical and mechanical properties of selected root canal sealers

To evaluate and compare the porosity, degree of conversion (DC) and hardness of two resin-based sealers; RealSeal and EndoRez, and a silicon-based sealer; GuttaFlow to that of a traditional zinc oxide-based sealer; TubliSeal. For porosity, four samples from each sealer were prepared and scanned using a SkyScan 1072 Micro-CT. Porosity was then calculated using specialized software. For DC, 10 samples from each sealer were prepared and placed onto a Fourier transform infrared spectroscopy spectrometer. Spectra readings were carried out before and after curing of the sealers, and the DC for each sealer was calculated. For hardness, 10 samples from each sealer were prepared and then tested using a Wallace hardness tester. SPSS software was used for statistical analysis of the data using one-way anova and independent t-tests. TubliSeal had the highest percentage porosity (3.52%), whilst RealSeal had the lowest percentage porosity (0.41%). Statistically significant differences (P = 0.01) in porosity were present between all groups except between RealSeal and EndoRez groups. RealSeal exhibited a significantly higher DC% than EndoRez (P = 0.01), whereas EndoRez had the highest hardness number [28.54 Vickers hardness number (VHN)] whilst TubliSeal showed the lowest (13.57 VHN). Statistically significant differences in hardness were found between all groups (P = 0.01) except between RealSeal and EndoRez groups. Resin-based sealers had less porosity, greater hardness and a high DC.

Microstructure and wear characteristics of hypereutectic Fe–Cr–C cladding with various carbon contents

Abstract The current study used flux core arc welding to produce a series of hypereutectic Fe–Cr–C claddings with various carbon content. Depending on the carbon content, this research produced hypereutectic microstructures of γ-Fe + (Cr,Fe)7C3 carbides. As the carbon content of a cladding increased from 3.73 to 4.85 wt.%, the surface fractions of carbides increased from 33.8% to 86.1%. The morphology of primary (Cr,Fe)7C3 carbides also transited from a blade-like to a rod-like shape. With regard to wear performance, the relationship between wear resistance and hardness (H) is non-linear. However, the mean free path (λ) of primary (Cr,Fe)7C3 carbides must be considered. Wear resistance is proportional to H/λ. The primary carbides can prevent the eutectic colonies from selective abrasion. The rod-like (Cr,Fe)7C3 carbides also provide much better wear resistance because rod-like carbides have a greater hardness. After an abrasive wear process, abrasive particles cause plastic plows when the cladding has lower surface fractions of carbides. The fracture of primary carbides leads into the craters where it occurs in the worn cladding surface with higher surface fractions of carbides.

Dislocation viscoplasticity aspects of material fracturing

Abstract Dislocation viscoplasticity, whether occurring before, during, or after the appearance of cracking, and with energy requirement additional to needed crack surface energy, has proved to be the bane of simplistic strength/energy evaluations applied to the fracturing properties of solid materials. George Irwin, in later years, turned his attention to such crack-effected viscoplasticity consideration in relation to the complex microstructural aspects of fracturing behaviors obtained for nuclear pressure vessel steels. The work is reviewed here with a broader research focus on dislocation plasticity aspects of fracturing behaviors, at ever smaller crack sizes, for a wider range of materials, especially, of relatively greater hardness.

Review of research work in sinking EDM and WEDM on metal matrix composite materials

Metal matrix composites (MMCs) are newly advanced materials having the properties of light weight, high specific strength, good wear resistance and a low thermal expansion coefficient. These materials are extensively used in industry. Greater hardness and reinforcement makes it difficult to machine using traditional techniques, which has impeded the development of MMCs. The use of traditional machinery to machine hard composite materials causes serious tool wear due to the abrasive nature of reinforcement. These materials can be machined by many non-traditional methods like water jet and laser cutting but these processes are limited to linear cutting only. Electrical discharge machining (EDM) shows higher capability for cutting complex shapes with high precision for these materials. The paper presents a review of EDM process and year wise research work done in EDM on MMCs. The paper also discusses the future trend of research work in the same area.

Application of high velocity impact welding at varied different length scales

Three complementary impact welding technologies are described in this paper. They are explosive welding, magnetic pulse welding, and laser impact welding, which have been used to provide metallurgical bonds between both similar and dissimilar metal pairs. They share the physical principle that general impact-driven welding can be carried out by oblique impact but are used at different length scales from meters to sub-millimeter. The different length scales require different kinds of systems to drive the process, and the scales themselves can give different weld morphologies. Metallographic analysis on cross-sections shows a wavy interface morphology which is likely the result of an instability associated with jetting, which scours the surfaces clean during impact. The normalized period and amplitude of the undulations increase with increasing impact energy density. Microhardness testing results show the impact welded interface has a much greater hardness than the base metals. This can lead to weldments that have strengths equal to or greater than that of the weakest base material.

Biocompatibility and water durability of alumina-zirconia ceramics blended with microsized HA particles

To improve the bioactivity of alumina containing yttria stabilized zirconia (Al-YSZ), composite ceramics consisting of Al-YSZ and 0–10 wt % of hydroxyapatite (HA) were prepared. The XRD patterns of sintered disks with an HA content above 3 wt % had monoclinic and cubic YSZ phases and a β-tricalcium phosphate phase. Although the Vickers hardness decreased as the HA content increased, all the prepared ceramics had the same or greater hardness (1000–1300 Hv with a load of 0.49 N) compared to typical YSZ ceramics (900–1000 Hv) commonly used in clinics. Furthermore, the bonelike apatite formation ability in simulated body fluid, which was examined as a screening of bioactivity, suggested that all the surfaces of Al-YSZ ceramics blending with a small amount of HA may possess the ability to connect bone. After the accelerated low temperature degradation (LTD) test performed in normal saline at 120°C for five days using composite ceramics with the HA content of 0, 1, 3, and 10 wt %, the tetragonal zirconia phase of all composite ceramics were partially transformed into the monoclinic phase with a transition ratio of ca. 16–18 mol % (for HA = 0 and 10 wt %) and ca. 4–5 mol % (for HA = 1 and 3 wt %). Blending microsized HA powder in Al-YSZ ceramics has both positive and negative effects on the LTD durability of Al-YSZ ceramics. An advantage is that calcium ion substitution in YSZ seems to stabilize the tetragonal (or cubic) zirconia phases, but the increased surface area exposed to the solution is a disadvantage.

Subsurface mechanical properties of polyurethane/organoclay nanocomposite thin films studied by nanoindentation

A series of the exfoliated or intercalated PU/organoclay nanocomposite thin films were prepared by in situ polymerization of polyol/organoclay mixture, chain extender and diisocyanate. The surface mechanical properties of the PU/organoclay nanocomposite films were investigated by means of nanoindentation. The results show that the hardness, elastic modulus and scratch resistant of the nanocomposites dramatically improved with the incorporation of organoclay. This improvement was dependent on the clay content as well as the formation structure of clay in the PU matrix. At 3% clay content, the hardness and elastic modulus of intercalated nanocomposites increased by approximately 16% and 44%, respectively, compare to pure PU. For exfoliated nanocomposite, the improvements in these properties were about 3.5 and 1.6 times higher than the intercalated ones. The exfoliated PU nanocomposites also had greater hardness and showed better scratch resistance compared to the intercalated ones.

Lutein-enriched frankfurter-type products: Physicochemical characteristics and lutein in vitro bioaccessibility

This paper reports a study of the physicochemical characteristics of lutein-enriched frankfurter-type products with two fat levels, and the lutein in vitro bioaccessibility in these products. In general, the high-fat products possessed better emulsion stability and greater hardness and chewiness than low-fat samples. For each fat level, the addition of lutein extract in olive oil reduced emulsion stability in meat products. The presence of lutein reduced the lightness and increased the redness of samples. Lutein was highly stable upon in vitro digestion, with overall recovery of over 84% at the end of the duodenal phase and very low isomerisation. Micellarisation was high but depended on the fat content, ranging from 29–34% (for the low-fat sample) up to 73–81% of the amount initially present (for the high-fat sample). Storage (22 days at 4 °C) did not significantly affect lutein content or bioaccessibility. Our results support the suitability of meat products as lutein carriers and as a means to increase the systematic intake of lutein.

Chalcogenide glass e-beam and photoresists for ultrathin grayscale patterning

The advantages and applications of chalcogenide glass (ChG) thin film photoresists for grayscale lithography are demonstrated. It is shown that the ChG films can be used to make ultrathin (~600 nm), high-resolution grayscale patterns, which can find their application, for example, in IR optics. Unlike polymer photoresists, the IR transparent ChG patterns can be useful as such on the surface or can be used to transfer the etched pattern into silicon or other substrates. Even if the ChG is used as an etch mask for the silicon substrate, its greater hardness can achieve a greater etch selectivity than that obtained with organic photoresists. The suitability of ChG photoresists is demonstrated with inexpensive and reliable fabrication of ultrathin Fresnel lenses that are transparent in the visible as well as in the IR region. The optical functionality of the Fresnel lenses is confirmed. Application of silver photodissolution in grayscale lithography for microelectromechanical systems (MEMS) applications is also shown. A substrate to ChG/silver thickness etching ratio of ~10 is obtained for the transfer of patterns into silicon using reactive ion etching (RIE), more than a fivefold increase compared to traditional polymer photoresist.

Structural relaxation and crystallization of NiTi thin film metallic glasses

This letter demonstrates the effects of structural relaxation on the crystallization and phase transformation behavior of NiTi thin films. Heat treatments below the glass transformation temperature produce films with a greater hardness than as-deposited films. The reduction in free volume occurring during film relaxation plays a role. Using scanning electron microscopy, structural relaxation was found to decrease the overall crystallization time and increase the nucleation rate, thus modifying the resulting microstructures. Structural relaxation had little effect on the phase transformation temperatures of fully crystallized films, but slightly increased the resulting actuation force during transformation.

The structure and mechanical properties of as-cast Zr–Ti alloys

This study has investigated the structure and mechanical properties of pure Zr and a series of binary Zr–Ti alloys in order to determine their potential application as dental implant materials. The titanium contents of these alloys range from 10 to 40 wt.% and were prepared by arc melting in inert gas. This study evaluated the phase and structure of these Zr–Ti alloys using an X-ray diffraction (XRD) for phase analysis, and an optical microscope for microstructure analysis of the etched alloys. Three-point bending tests were performed to evaluate the mechanical properties of all specimens. The experimental results indicated that the pure Zr and Zr–10Ti comprised entirely of an acicular hexagonal structure of α′ phase. When the Ti content increased to 20 wt.%, a significant amount of β phase was retained. However, when the Ti content increased to 40 wt.%, only the equi-axed, retained β phase was observed in the cast alloy. Moreover, the hardness values and bending strengths of the Zr–Ti alloys decreased with an increasing Ti content. Among pure Zr and Zr–Ti alloys, the α′-phase Zr–10Ti alloy has the greatest hardness and bending strength. The pure Zr and Zr–Ti alloys exhibit a similar elastic modulus ranging from 68 GPa (Zr–30Ti) to 78 GPa (Zr–40Ti). Based on the results of elastic moduli, pure Zr and Zr–Ti alloys are found to be suitable for implant materials due to lower modulus. Like bending strength, the elastically recoverable angle of Zr–Ti alloys decreased as the concentration of Ti increased. In the current search for a better implant material, the Zr–10Ti alloy exhibited the highest bending strength/modulus ratios as large as 25.3, which are higher than that of pure Zr (14.9) by 70%, and commercially pure Ti (8.7) by 191%. Thus, Zr–Ti alloy's low modulus, ductile property, excellent elastic recovery capability and impressive strength confirm that it is a promising candidate for dental implant materials.

Index test for the degradation potential of carbonate sands during hydraulic transportation

Carbonate sands undergo degradation when transported hydraulically from a dredging vessel to the reclamation site. Risks involved in the production of fines during hydraulic transport are a deterioration of the mechanical properties of the fill in certain areas of the reclamation area where these fines concentrate. In order to assess sand degradation in the concrete and road construction industry, the Micro-Deval test for fine aggregates was developed in France and Canada. During Micro-Deval testing, aggregates degrade when tumbled in a rotating steel drum with water and steel balls. In the Canadian standard, the steel charge is lower than in the French standard and balls have the diameter of the smallest balls used in the French test. During testing, the quantity of fines produced is measured. This makes the Micro-Deval test an option for assessing the degradation of sand during hydraulic transportation of slurries in the dredging industry. Three sands are tested: two shelly carbonate sands and one quartzic river sand for comparison. The carbonate sands were sampled on reclaimed land and had been subjected to hydraulic transportation in pipeline before artificial deposition. Due to differences in particle shape, the carbonate sands and the quartz sand have a different number of contacts with the steel charge in the drum of the Micro-Deval and are not exposed to the same degradation forces during testing. It was found that the quartzic sand suffers relatively much degradation as compared to the carbonate sands, despite its greater hardness and resistance to crushability. The French test appears to create turbulence that promotes floatation of the curved shells of the carbonate sands instead of shell grinding at the bottom of the drum by contact with the steel balls. Microscopic observations of sand samples before and after testing showed that the French Micro-Deval test is too destructive. The test leads to the fragmentation by impact of the quartz sands and the destruction of certain particle types that had survived hydraulic transportation. With respect to the Canadian test, microscopic examination of sand grains before and after testing shows there is still much fragmentation of quartz grains. A lower rotational speed combined with a limited steel charge made of uniform balls of a smaller diameter, reduces turbulence, shell floatability and last but not the least, impact forces. It produces the desired result: a high Micro-Deval loss for the carbonate sands in comparison to that for the quartz sands and a very limited fragmentation of the quartz grains. Once the slurry reaches its destination, the grain size distribution of the fines fraction will influence the mechanical behaviour of mixed sands. A procedure is proposed to measure the particle size distribution of the fines fraction produced during Micro-Deval testing. Field validation is needed to validate preliminary laboratory results.

Optimal Contraction Theorem for Exploration–Exploitation Tradeoff in Search and Optimization

<para xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> Global optimization process can often be divided into two subprocesses: exploration and exploitation. The tradeoff between exploration and exploitation (<emphasis emphasistype="boldital">T:Er&amp;Ei</emphasis>) is crucial in search and optimization, having a great effect on global optimization performance, e.g., accuracy and convergence speed of optimization algorithms. In this paper, definitions of exploration and exploitation are first given based on information correlation among samplings. Then, some general indicators of optimization hardness are presented to characterize problem difficulties. By analyzing a typical contraction-based three-stage optimization process, <emphasis emphasistype="boldital">Optimal Contraction Theorem</emphasis> is presented to show that <emphasis emphasistype="boldital">T:Er&amp;Ei</emphasis> depends on the optimization hardness of problems to be optimized. <emphasis emphasistype="boldital">T:Er&amp;Ei</emphasis> will gradually lean toward exploration as optimization hardness increases. In the case of great optimization hardness, exploration-dominated optimizers outperform exploitation-dominated optimizers. In particular, random sampling will become an outstanding optimizer when optimization hardness reaches a certain degree. Besides, the optimal number of contraction stages increases with optimization hardness. In an optimal contraction way, the whole sampling cost is evenly distributed in all contraction stages, and each contraction takes the same contracting ratio. Furthermore, the characterization of optimization hardness is discussed in detail. The experiments with several typical global optimization algorithms used to optimize three groups of test problems validate the correctness of the conclusions made by <emphasis emphasistype="boldital">T:Er&amp;Ei</emphasis> analysis. </para>