Graphene Oxide-Based Composite Organohydrogels with High Strength and Low Temperature Resistance for Strain Sensors

In the recent years, a rapid development of the polymeric hydrogel-based sensors has been witnessed. However, conventional hydrogels often exhibit poor mechanical properties. Additionally, the use of these sensors at...

CUTTING STONE BUILDING MATERIALS WITH CUT WHEELS OF CUBIC BORON NITRIDE

The advantage of cutting stone building materials with SSM (synthetic superhard materials) wheels is that, first of all, it is possible to obtain high processing productivity and dimensional stability, which are 3..5 and 50…100 times higher than those of traditional tools based on carborundum, respectively. The study of the process of cutting stone materials with CBN (cubic boron nitrite) wheels is aimed at establishing force dependences, determining the cutting power and heating temperature of the cutting disc during operation. The forces were measured using a tensometric dynamometer UDM-50. To measure and calculate the cutting temperature, a thermoelectric method based on the formation of practically not inertial microthermocouples during cutting was used. The temperature to which the CBN cutting wheel on a metal base is heated is a limiting factor in processing, since when heated to a temperature of 600ºС, the strength of the wheel decreases by half, which can cause its rupture under the action of centrifugal forces, as well as loss of stability and jamming during cutting. In the present study, the wheel temperature was measured after one minute of continuous operation. The values of the component of the cutting force PY, depending on the processing modes, can reach values of the order of 70 N. The values of the component of the cutting force PZ, depending on the processing modes, can reach values of 45 N. The cutting power can be 2800W. The temperature resistance of the wheel (heating time of the wheel up to 600ºС) when cutting dry is maximum 28 minutes, when grinding with cooling of the cutting zone with negative temperature air from a Ranque-Hilsch tube, the temperature resistance is 35 minutes, with ejector cooling of sprayed coolant 37 minutes and with jet-pressure cooling it is 40 minutes. The maximum cutting length is respectively 0.7: 0.8; 0.9 and 2m. The cutting power is 600...2800W.

Incorporation of Partially Hydrolyzed Polyacrylamide With Zwitterionic Units and Poly(Ethylene Glycol) Units Toward Enhanced Tolerances to High Salinity and High Temperature

Partially hydrolyzed polyacrylamide (HPAM) was widely implemented to improve the rheological properties of displacing fluids, but the high temperature and salinity of the reservoir brine limited their applications. Herein, copolymers including HPAM, zwitterion-modified HPAM (z-HPAM), PEG-modified HPAM (p-HPAM), and zwitterion/PEG-modified HPAM (zp-HPAM) were prepared by free radical polymerization in an aqueous solution. The viscosity of these copolymers under different temperature and salinity was measured in aqueous solution. It is found that the viscosity of the HPAM under the harsh condition (90oC, 20 × 104 mg/L salinity) is only 9.6% of that value under the normal condition (25oC, pure water), while the z-HPAM can significantly improve salt resistance by the effects of salting-in effect and intermolecular electrostatic crosslinking, showing a viscosity retention of 22.9% under the harsh condition. The addition of PEG-containing monomer can strengthen hydrogen bonding between the polymer chains and form a sterically ordered structure with improved salinity and temperature resistance. The synergistic effect of zwitterion units and PEG units endows the zp-HPAM with good salinity and temperature resistance; thus, the sample viscosity under the harsh condition remains 170 mPa s, which retains 29% of the value under the normal condition. The enhanced rheology properties of the zp-HPAM under the harsh condition are significant for the enhanced oil recovery of water-soluble polymer flooding.

Nano-SiO2/hydroxyethyl cellulose nanocomposite used for 210 °C sedimentation control of petroleum drilling fluid

Cellulose derivatives are widely applied in the field of oil and gas exploration. However, this kind of natural polymers always shows poor temperature resistance due to their organic nature. To improve the temperature resistance of hydroxyethyl cellulose (HEC), inorganic nano-SiO2 was introduced onto HEC polymer chains through the silylation coupling technique. And Fourier transform infrared spectrum (FTIR), X-ray photoelectron spectrum (XPS), and thermogravimetic analysis (TGA) were used to analyze the nanocomposite. As a result, nano-SiO2 particle is chemically coupled onto hydroxyethyl cellulose molecule, and nano-SiO2/hydroxyethyl cellulose nanocomposite (RJ-HEC) shows excellent thermal stability comparing with HEC polymer. In experiment, thermal aging tests were utilized, and test results suggest that nano-SiO2/hydroxyethyl cellulose (RJ-HEC) nanocomposite can be utilized as thickening agent of water-based drilling fluid, which shows improved rheology stability at 210 °C and excellent salt (NaCl) tolerance.

ZIF-8/PI Nanofibrous Membranes With High-Temperature Resistance for Highly Efficient PM0.3 Air Filtration and Oil-Water Separation

Air and water pollution poses a serious threat to public health and the ecological environment worldwide. Particulate matter (PM) is the major air pollutant, and its primary sources are processes that require high temperatures, such as fossil fuel combustion and vehicle exhaust. PM0.3 can penetrate and seriously harm the bronchi of the lungs, but it is difficult to remove PM0.3 due to its small size. Therefore, PM0.3 air filters that are highly efficient and resistant to high temperatures must be developed. Polyimide (PI) is an excellent polymer with a high temperature resistance and a good mechanical property. Air filters made from PI nanofibers have a high PM removal efficiency and a low air flow resistance. Herein, zeolitic imidazolate framework-8 (ZIF-8) was used to modify PI nanofibers to fabricate air filters with a high specific surface area and filtration efficiency. Compared with traditional PI membranes, the ZIF-8/PI multifunction nanofiber membranes achieved super-high filtration efficiency for ultrafine particles (PM0.3, 100%), and the pressure drop was only 63 Pa. The filtration mechanism of performance improvement caused by the introduction of ZIF-8/PI nanofiber membrane is explored. Moreover, the ZIF-8/PI nanofiber membranes exhibited excellent thermal stability (300 C) and efficient water–oil separation ability (99.85%).