The Characteristics of Nitinol in Spinal Implant Manufacturing

: Due to the increasing number of diseases related to the spine, we expect to see more research on the implants used in this area. These implants should have features such as strength, fatigue resistance, chemical stability and biocompatibility, which fortunately are seen in an alloy called nitinol. In this study, six lumbar vertebral implants were made of nitinol and these samples been studied by some experiments such as: X-ray diffraction and biocompatibility (evaluation of cytotoxicity by MTT assay). Finally, we came to the conclusion that the mentioned alloy with suitable microstructure is appropriate for medical applications specially as an orthopedic implant. According to the X-ray diffraction pattern, the samples have austenitic structures in the room temperature and the predominant phase of the porous sample is B2-NiTi. Since the sample should be biocompatible after placement in the body and should not cause an immune system reaction, this test was also examined and the samples were tested in vitro with an MTT kit and the biocompatibility was assessed. The results of biocompatibility tests also indicate the suitability of the implant in terms of cellular characteristics. These properties have made this alloy superior to other alloys in orthopedic implant utilization, especially in areas under continuous loading. It is hoped that the construction of this type of implant will pave the way for facilitating the treatment of spinal abnormalities.

DETERMINATION AND STUDY OF THE VOLUME AND DENSITY OF COMPLEX POROUS SAMPLES

Various porous materials are widely used in various industries, such as chemical, metallurgical, energy, light, food, etc. Therefore, a comprehensive study of their structure and physical and technical properties is of great scientific and technological importance. The article presents the results of determining and studying the volume and density of porous sample materials using a new experimental method. The determination of the volume and density of waterproof samples of any complex shape can be easily determined on the basis of Archimedes ' law. However, it is impossible to determine the volume and density of porous water-absorbing samples of complex shape directly using this law. The article presents new experimental methods (methods) for determining the volume and density of such porous samples of complex shape. The results of experimental work carried out using the proposed new methods are presented and analyzed.

Development and Mechanical Testing of Porous-Lightweight Geopolymer Mortar

In this study, a novel porous geopolymer mortar (GP) was produced and tested experimentally. Industrial waste materials/by-products were used as constituents of the GP, along with dune sand. One sample was produced as a control sample for benchmarking. For the rest of the samples, 15%, 30%, and 45% by volume, the solid constituents were replaced with expanded polystyrene foam (EPS) beads. These mortar samples were heat cured to depolymerize the EPS to cause porosity inside the samples. Indoor experiments were conducted to evaluate the response of produced porous GP to high heat flux. The porous samples were able to reduce heat transmission across the opposite surfaces. Induced porosity resulted in a decrement in compressive strength from 77.2 MPa for the control sample to 15.8 MPa for 45% porous sample. However, the limit lies within the standards for partitioning walls in buildings and pavements in urban areas to absorb rainwater.

Development and Mechanical Testing of Porous-Lightweight Geopolymer Mortar

In this study, a novel porous geopolymer mortar (GP) was produced and tested experimentally. Industrial waste materials/by-products were used as constituents of the GP, along with dune sand. One sample was produced as a control sample for benchmarking. For the rest of the samples, 15%, 30%, and 45% by volume, the solid constituents were replaced with expanded polystyrene foam (EPS) beads. These mortar samples were heat cured to depolymerize the EPS to cause porosity inside the samples. Indoor experiments were conducted to evaluate the response of produced porous GP to high heat flux. The porous samples were able to reduce heat transmission across the opposite surfaces. Induced porosity resulted in a decrement in compressive strength from 77.2 MPa for the control sample to 15.8 MPa for 45% porous sample. However, the limit lies within the standards for partitioning walls in buildings and pavements in urban areas to absorb rainwater.

Capillary Scanning of a Porous Matrix. Experimental Techniques and Processing of its Results

The article presents an analysis of the possibilities of the previously unused method for the experimental study of porous permeable materials and the determination of their structural characteristics. The purpose of the experiment is to determine the geometric parameters of the porous matrix, which integrates the characteristics of the porous material. An example of analytical scanning of a porous structure is considered. A review of existing experimental methods is given. A scheme of the experimental setup, methods for conducting a capillary experiment and processing the data obtained are proposed. As an example, a mathematical model of the experiment is used, illustrating the possible results of the study of a porous sample. It is shown how the results of experiments are transformed into a porous matrix and are interpreted as its capillary scanning. It is proved that this model of porous structure can be used as a starting position in the mathematical calculations of the processes occurring in porous structures.

Development of method for determination of the kinetics constants of coal char gasification in pore diffusion regimes

In this paper, we developed a method for determining the kinetic constants of partially diffusion-controlled heterogeneous reactions in a porous sample of powder. Studies have been conducted on the experimental data of thermogravimetric analysis of carbon conversion in a stream of CO2, using a new method of processing kinetic curves, to obtain updated values of the kinetic constants under conditions where widely used models are inappropriate. Data obtained can be used for a reliable assessment of the characteristics of the gasification process.

Porous substrate affects a subsequent attachment ability of the beetle Harmonia axyridis (Coleoptera, Coccinellidae)

According to literature data, porous substrates can cause a reduction of insect attachment ability. We carried out traction experiments with adult ladybird beetles Harmonia axyridis on the smooth solid glass sample and rough porous Al 2 O 3 membrane to prove the primary effect of absorption of the insect pad secretion by porous media, rather than surface roughness, on the attachment force on the porous sample. With each insect individual, a set of five experiments was conducted: (1) on glass; (2) on the porous membrane; (3–5) on glass immediately after the test on the porous surface, then after 30 min and 1 h of recovery time. On the porous substrate, the forces, being similar in females and males, were greatly reduced compared to those measured on glass. A significant difference between the force values obtained in the first (before the test on the porous sample) and second (immediately after the experiment on the porous sample) tests on glass was observed. After 30 min recovery time, beetles completely regained their attachment ability. Females produced significantly lower forces than males in all experiments on glass: the differences are probably caused by the sexual dimorphism in the microstructure of their adhesive pads. The obtained results are of fundamental importance for further application in biomimetics of novel insect-repelling surfaces and in plant protection by using porous materials.

Porous Resorcinol-Formaldehyde Resins

Porous ion-exchanging resorcinol-formaldehyde resins were prepared by removing an inorganic template (CaCO3) and by polymerization of a highly concentrated emulsion with toluene as a dispersing phase. As compared to original resorcinol-formaldehyde resins, the porous one is characterized with higher values of internal diffusion, providing exceptional purification coefficients. However, the amounts of the introduced CaCO3 and toluene have to be below 10 wt.% and 25 wt.%, respectively, to avoid fast degradation of the ion-exchanger. Under dynamic conditions, average purification coefficients in the model solution of Cs-137 are twice higher than those of the non-porous sample. The prepared porous ion-exchange resin can be used in cases when high Cs-137 uptake from liquid media should be realized at increased rates of solution percolation.