Papers by Keyword: Density

Abstract: The influence of different factors in the alcogel preparation process and ambient pressure drying process on packing density of hydrophobic TiO₂ aerogel synthesized by ambient pressure drying (APD) and the optimum preparation conditions were investigated by the orthogonal test with four-factor and three-level L₉(3⁴), respectively. The morphology and structural properties of hydrophobic TiO₂ aerogels with different density were characterized by Fourier Transform Infrared Spectroscopy (FT-IR), Thermogravimetry (TG), N₂ adsorption-desorption measurement and Scanning Electron Microscope (SEM). The results showed that the most important factors in the preparation process for TiO₂ aerogels with low-density under ambient pressure are aging time, the volume ratio of C₂H₅OH to TBT, ethanol immersion time and hydrophobic modification time. The optimized preparation conditions are that aging time is 24 h, the volume ratio of C₂H₅OH to TBT is (7+7) : 5, the volume ratio of H₂O to TBT is 1.7 : 5, the volume ratio of HAc to TBT is 1.7 : 5, ethanol immersion time is 24 h, hydrophobic modification time is 48 h, hexane solvent replacement time is 24 h and the drying temperature is 393 K. TiO₂ aerogels with density of 460 kg/m³ was obtained at the optimized conditions. TiO₂ aerogel with lower density displays higher specific surface area, porosity and pore volume as well as the larger pore size.

Abstract: Nondestructive determination of Au in gold ornaments mainly takes density method and X ray fluorescence spectrometer with energy dispersion (EDXRF), which exists disadvantages. This paper based on the principle of crystallography, deduced the mathematical relationship between the crystallographic parameters, the density and the impurities content in gold jewelry alloys, then introduced the results by density testing and determination of Ag and Cu by EDXRF into the mathematical relationship, and obtained the gold weight percent in gold jewelry alloys. The results show that obtained the gold weight percent and determination of Au by fire assay are almost consistent, which the error is less than 0.12 %, so establishes a synthesis method of determination of Au by EDXRF and density testing, solves the disadvantages which EDXRF only detects on gold jewelry surface and small area, and density testing cannot detect gold jewelry alloy and demands that jewelry shape is simple, and provides an effective synthesis way for determination of Au in gold jewelry alloys.

Abstract: Drilling through depleted zones and weak formation can prove troublesome since the fracture resistance reduces from its normal boundary [1]. To successfully drill a hole section requires the selection of a low density cement slurry to prevent loss circulation while not exceeding the fracture resistance of the formations exposed. Large number of loss circulation will greatly impact the drilling cost and rig time. This research is focusing on the performance studies of lightweight oilwell cements using foam and cenosphere as the lightweight agents. All tests were conducted according to API Recommended Practice 10B-2. Three performance tests have been conducted such as density test, free water test and compressive strength test. The comparison was made at different percentage of lightweight agents e.g. 10, 20, 30 and 40 percent by weight of cement (%BWOC) respectively. The findings show the performances of formulated foam cement and cenosphere cement are within API limit. However, foam cement can reduce the density of set cement in about 8% greater than the cenosphere cement.

Abstract: Al/(SiCw+Al₂O₃p) composite was a blend of fine aluminum powder serving as a matrix while Silicon Carbid whiskers (SiCw) and Alumina (Al₂O₃p) as a reinforcement. Powder metallurgy was used for the manufacture of composites according to the shape of the test specimen. Parameter testing was conducted with varied sintering holding time of 1 h, 3 h and 6 h at a sintering temperature of 500°C and 600°C. This study was conducted to know hardness properties, density, porosity and SEM analysis. The results show that the sintering process which has been conducted affects the physical and mechanical properties of the composite. Increased hardness and density occur due to the stronger or more dense interface bonding between matrix and reinforcement which are affected by the increase in the holding time and sintering temprature, where the highest is at 6 hours with 600°C, while the porosity decreases inversely proportional to the density and the hardness that occur in composite materials.

Abstract: In the processing of semiconducting electro ceramic materials the use of appropriate binder can lead to improve characteristics of powder which will reduce density gradient in the green body during compaction. The binder system is anticipated to have an influence on the grain growth and microstructure which in turn affect the electrical performance. To investigate this phenomenon, TiO₂ powder doped with tungsten oxide (WO₃), silicon oxide (SiO₂) and bismuth oxide (Bi₂O₃) was processed with and without various percent of latex binder. The prepared samples were characterized by evaluating the physical properties like green density, fired density, axial and radial shrinkage, micro hardness and compressive strength. It was observed that TiO₂ processed with latex binder exhibited higher green density and less axial and radial shrinkage compared to powder processed without binder. However, the binder level did not have any significant influence on the other characteristics of varistor discs. SEM analysis indicated that the average grain size was also influenced by the percent of binder used and but the higher average grain size was obtained for discs without any binder.

Abstract: Nowadays, people have built mega-watt scales of wind turbines to generate electricity from wind energy. These big scales of wind turbine blade need lighter materials in order to optimize the generation of electricity. Due to this issue, purpose of this paper is to find a light material which is suitable to be used in making wind turbine blades. The use of natural fiber as a reinforcement agent in composite seems to have a big potential as natural fibers show desired characteristic needed for wind turbine blades' material. In this research, rice straw fiber was used as reinforced agent in composite with polypropylene as matrix. The composite produced was then characterized by mechanical testing which include tensile, flexural and impact as well as density measurement, dynamic mechanical testing (DMA) and Scanning Electron Microscopy (SEM). From the result obtained, it is found that the introduction of rice straw fiber to polypropylene matrix able improve the mechanical properties of the composite. The results of the composite obtained were then compared with current materials used.

Abstract: (0, 5, 10, 15, 20) vol% CBN-WC/Co composites were consolidated by ball milling and the following hot-pressing sintering method. WC, Co and CBN powders were used as the starting materials. The effects of the CBN content on the density, microstructure and mechanical properties of CBN-WC/Co composites were investigated. The results showed that the CBN content had remarkable influence on the microstructure and mechanical properties of CBN-WC/Co Composites. With the increasing content of CBN, the density decrease, while Vickers hardness and flexural strength increased initially to the maximum values and then decreased at CBN 10 vol%. When 10 vol% CBN-WC/Co powders were hot-pressing sintered at 1350°C and 20MPa for 90 min, an excellent Vickers hardness of 19.8GPa was achieved, combining a flexural strength of 682MPa.

Abstract: High hardness, good thermal and electrical conductivity make carbides technologically important materials. The high melting temperature and low coefficients of self-diffusion make it difficult to obtain full dense material. In this paper the results of Spark Plasma Sintering (SPS) of transition metal carbides: NbC, TaC, TiC, ZrC, VC with the addition of graphene 10-20 nm x 14 microns in an amount of 2.5 mass % are presented. Powders were mixed in isopropyl alcohol in a planetary ball mill for 1h. The sintering processes was carried out at 2200°C at two different times: 5 and 30 min. Microstructure of the samples was analyzed using scanning electron microscopy. The measurements of density, Young's modulus hardness and electrical properties were carried out, also. The best properties were obtained for titanium carbide powder, sintered for 30 min. The most significant density increase of the sintered carbide–graphene composite by about 5.3% (depending on increasing sintering duration) was obtained for niobium carbide, while the smallest densities change for zirconium carbide.

Abstract: The researches have been focused on composite materials area, especially hybrid metal matrix composites. A hybrid composite has two or more reinforcing elements and improved properties according to the reinforcing elements used.This paper aims to discuss the Al/Al₂O₃+Gr_p behavior at different pressing forces. The composite was processed by a powder metallurgy route. Alumina used as reinforcing material provides a high strength and hardness and graphite provides lubricating properties. The results show that the compressed un-granulated powder has a higher tendency to fracture than the granulated powder. The compressed powder density was almost constant after a pressing force of 600 MPa.

Abstract: The utilization of waste materials which are abundant and cheap, especially from clean resources, has become more pressing than ever. This paper, discusses the utilization of the wastes in the form of palm oil fuel ash and oil palm kernel shell in the production of mortar mixes as a part of new and innovative materials in construction industry. The studies include the basic properties including the morphology of the composite with regards to variations in the mix design process. In order to get a better performance in terms of strength development, the ash used has gone through heat treatment and ground up to the size less than 2µm. High volume of 60%, 80% and 100% palm oil fuel ash was used as cement replacement. The incorporation of more than 80% of palm oil biomass waste as cement and sand replacement has produced mortar having an improved compressive strength than normal mortar. In addition, the density of the mortar with biomass waste was less than normal mortar. Overall results have revealed that the inclusion of high volume palm oil biomass waste can produce mortar mix with high strength, good performance and most importantly more sustainable.