Exploring the Surface Chemistry for the Stabilization of Bismuth Titanate Fine Particle Suspensions in Cement Systems

ABSTRACT: Introduction. The evolution of the construction industry in its current stage calls for the alteration of traditional building materials through the incorporation of nano- and fine-dispersed additives. These additions confer new, unique attributes to cement-based construction materials, enabling control over structure formation processes. Consequently, this allows for the creation of materials with specifically defined characteristics. Additives can be introduced into the cement composite during the joint grinding with clinker minerals, as a component of dry building mixture, or in the form of a suspension instead of mixing water. Therefore, it is essential to obtain fine particles suspensions resistant to aggregation and sedimentation. Thus, the purpose of this study is to obtain stabilized suspensions of bismuth titanate fine particles for cement systems and to study the properties of modified cement stone. Materials and methods. The purpose of this work was to establish the optimal concentration of polycarboxylate plasticizer in industrial water, necessary for the stabilization of fine bismuth titanate suspensions using surface tension and conductometric determination methods, the sedimentation stability of the obtained suspensions and the effect of ultrasonic exposure, as well as the physical and mechanical characteristics of cement stone modified with the obtained suspensions. Results and discussion. In order to establish the optimal concentration of the plasticizer necessary to obtain stable suspensions of bismuth titanate particles, the critical micelle concentration (CMC) for the plasticizer was determined with tap water as the dispersed medium. The CMC value was 1.3 g/l. If the concentration exceeds CMC, the process of micelle formation begins. In the micellar form, the plasticizer no longer provides stabilizing effect on the additive particles, therefore, the concentration of the plasticizer should be lower than the CMC. It was also found that ultrasound exposure increases the sedimentation stability of suspensions. The resulting stabilized suspensions were used instead of mixing water to obtain modified cement stone samples. There is an increase in the compressive strength of cement stone samples obtained after the introduction of fine bismuth titanate into the cement composite in the form of water suspensions stabilized by ultrasonic treatment with concentrations of 10, 30 and 50 g/l. The increase in compressive strength of modified samples compared to reference sample was from 24 to 33 MPa at first day age (by 13, 25 and 38% respectively), and from 80 to 93 MPa at 28 days age (by 4, 9 and 16%). Compressive strength of samples modified with bismuth titanate suspensions after ultrasonication compared to reference sample with plasticizer increased mostly at the first and third days age: from 29 to 42 MPa (by 31, 38 and 45%) and from 53 to 70 MPa (by 28, 30 and 32%) respectively. Conclusion. As a result of the research carried out in this study, the Critical Micelle Concentration (CMC) of a polycarboxylate plasticizer was determined, optimal for stabilizing fine-dispersed additive of bismuth titanate for cement systems, the effectiveness of ultrasonic treatment to achieve sedimentation stability of the obtained suspensions of the additive was confirmed, an increase in the strength characteristics of modified cement stone samples was established both in the initial hardening periods and at 28 days age. The results allow to consider a cement composite with fine bismuth titanate as a basis for obtaining building materials of new generation

Methodological Substantiation of the choice for a stabilizer for bismuth titanate fine particles suspensions

ABSTRACT: Introduction. The current stage of the construction industry and building materials science development involves the introduction and widespread application of nano- and fine particles capable of improving the properties of traditional materials. However, it is necessary to provide stabilization of nano- and fine-dispersed components in the cement system. Plasticizing additives can be used as stabilizers. It is important to set their concentration. Therefore, the purpose of this study is outlined, which lays in the methodological substantiation the stabilizing effect of various types of plasticizers on the suspension of fine synthetic bismuth titanate used in the modification of cement systems, and the establishment of the limits of their optimal concentrations. Materials and methods. The research is aimed at establishing the limits of optimal concentrations of polycarboxylate and sulfonaphthalene formaldehyde plasticizers. The limits of plasticizers optimal concentrationsis determined withdye solubilization method, surface tension and conductometric methods, and studies on establishing the stabilizing effect of plasticizers on a bismuth titanate fine particles suspension. Results and discussion. To establish the limits of the optimal concentration capable of stabilizing fine particles of bismuth titanate in suspension, CMC is determined by the dye solubilization method, surface tension and conductometric methods. It is found that a polycarboxylate plasticizer is characterized by one CMC point, and a sulfonaphthalinformaldehyde plasticizer is characterized by two CMC points: CMC1 and CMC2. At CMC1 point unstable spherical micelles are formed, which turn into stable ones at the CMC2 point. At concentrations exceeding the CMC2 value, polymorphic transformations of spherical micelles into nonspherical asymmetric micelles occur. The same can be traced for the polycarboxylate plasticizer CMC only in one stage. It can also be concluded that it is not reasonable to increase the plasticizer concentration above CMC for polycarboxylate plasticizer and above CMC2 for sulfonaphthalinformaldehyde plasticizer, which is due to structural changes in the micelles of plasticizers. It is assumed that in order to stabilize bismuth titanate fine particles, it is necessary to choose the plasticizers concentration within the limits not exceeding the values of CMC for polycarboxylate plasticizer and CMC2 for sulfonaphthalinformaldehyde plasticizer. Conclusion. Concluding results demonstrate the limits of optimal plasticizers concentrations for the stabilization of bismuth titanate fine particles suspension. For polycarboxylate plasticizer this range of concentrations is 1.1 – 1.5 g/l; for sulfonaphthalinformaldehyde plasticizer its 2.2 – 4.0 g/l

Self-compacting concrete as a modern solution to small architectural forms

Modern Materials science in Сonstruction is developing in a way of higher functionality, durability, ecological safety of the materials, which also must be easy to work with. The workability of concrete is provided by its property to fill the formwork under the influence of gravity. Small architectural forms (SAF) – are practical and art objects which complement outdoor spaces and enrich architectural, urban and landscape composition of the city. Manufacturing of SAF is complicated by its extraordinary geometric shapes with plenty of tiny elements. This fact limits the usage of traditional technologies of vibration for compaction. In this paper properties and composition of self-compacting concrete (SCC) are discussed, as well as the possibility of its application for thin-walled heavily reinforced constructions to produce unique SAF for landscape design. The obtaining of flowable segregation-resistant concrete mix with low water-cement ratio is studied. The hypothesis of applicability of SCC for SAF in landscape design is based on high deformability, flowability and consolidation by means of its own weight without segregation. The methodology of the research is based on the literature review concerning the usage of SCC for SAF with some special additives with plasticizing and anti-segregating affects. The investigation showed that SCC is applicable for SAF in landscape design

Sex-specific stress response and HMGB1 release in pulmonary endothelial cells

Women are known to be associated with a higher susceptibility to pulmonary arterial hypertension (PAH). In contrast, male PAH patients have a worse survival prognosis. In this study, we investigated whether the contribution of sex goes beyond the effects of sex hormones by comparing the ability of isolated male and female pulmonary endothelial cells to respire, proliferate and tolerate the stress. Mouse lung endothelial cells (MLEC) were isolated from the lungs of male and female 3-week old mice. Male MLEC showed an increased basal mitochondrial respiration rate, elevated maximal respiration, a significantly greater level of mitochondrial polarization, and a higher rate of proliferation. Exposure of cells to hypoxia (2% of O-2 for 24 hours) induced a strong apoptotic response in female but not male MLEC. In contrast, treatment with mitochondrial respiratory Complex III inhibitor Antimycin A (AA, 50 mu M) mediated severe necrosis specifically in male MLEC, while female cells again responded primarily by apoptosis. The same effect with female cells responding to the stress by apoptosis and male cells responding by necrosis was confirmed in starved pulmonary endothelial cells isolated from human donors. Elevated necrosis seen in male cells was associated with a significant release of damage-associated alarmin, HMGB1. No stimuli induced a significant elevation of HMGB1 secretion in females. We conclude that male cells appear to be protected against mild stress conditions, such as hypoxia, possibly due to increased mitochondrial respiration. In contrast, they are more sensitive to impaired mitochondrial function, to which they respond by necrotic death. Necrosis in male vascular cells releases a significant amount of HMGB1 that could contribute to the pro-inflammatory phenotype known to be associated with the male gender.Open access journalThis item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at [email protected]

Novel benzylidene-thiazolidine-2,4-diones inhibit Pim protein kinase activity and induce cell cycle arrest in leukemia and prostate cancer cells

The Pim protein kinases play important roles in cancer development and progression, including prostate tumors and hematologic malignancies. To investigate the potential role of these enzymes as anticancer drug targets, we have synthesized novel benzylidene-thiazolidine-2,4-diones that function as potent Pim protein kinase inhibitors. With IC 50 values in the nanomolar range, these compounds block the ability of Pim to phosphorylate peptides and proteins in vitro and, when added to DU145 prostate cancer cells overex-pressing Pim, inhibit the ability of this enzyme to phosphorylate a known substrate, the BH 3 protein BAD. When added to prostate cancer cell lines, including PC3, DU145, and CWR22Rv1, and human leukemic cells, MV4;11, K562, and U937 cells, these compounds induce G 1 -S cell cycle arrest and block the antiapoptotic effect of the Pim protein kinase. The cell cycle arrest induced by these compounds is associated with an inhibition of cyclin-dependent kinase 2 and activity and translocation of the Pim-1 substrate p27 Kip1 , a cyclin-dependent kinase 2 inhibitory protein, to the nucleus. Furthermore, when added to leukemic cells, these compounds synergize with the mammalian target of rapamycin inhibitor rapamycin to decrease the phosphorylation level of the translational repressor 4E-BP1 at sites phosphorylated by mammalian target of rapamycin. Combinations of rapamycin and the benzylidene-thiazolidine-2,4-diones synergistically block the growth of leukemic cells. Thus, these agents represent novel Pim inhibitors and point to an important role for the Pim protein kinases in cell cycle control in multiple types of cancer cells