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Relevant bibliographies by topics / Amorphous substances

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Academic literature on the topic 'Amorphous substances'

Author: Grafiati

Published: 4 June 2021

Last updated: 29 July 2024

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Journal articles on the topic "Amorphous substances"

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Antosik, Agata, Joanna Szafraniec, Krzysztof Niwiński, and Renata Jachowicz. "Amorphous drug substances." Farmacja Polska 74, no. 11 (November 30, 2018): 671–78. http://dx.doi.org/10.32383/farmpol/118638.

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Wang, Bo, and Yuan Ming Song. "Study on the Difference of Amorphous Substances of Coal Ashes." Advanced Materials Research 287-290 (July 2011): 1189–92. http://dx.doi.org/10.4028/www.scientific.net/amr.287-290.1189.

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There is much difference among the amorphous substances of different coal ashes, the important basis for their utilization. The micromorphology and content of the amorphous substances were measured by scanning electron microscopy (SEM) and chemical method respectively, and the 28d compressive strength ratio was also used to characterize their contribution to the cement-coal ashes system. The results show that the amorphous substances of BFBC/CFBC ashes are irregular and loose textured, which are significantly different from those of PC fly ashes that are spherical and compact. The content and the pozzolanic activity of the amorphous substance of BFBC ashes are greater than that of PC fly ashes.

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Shklovskii, V. A., and V. M. Kuz'menko. "Explosive crystallization of amorphous substances." Uspekhi Fizicheskih Nauk 157, no. 2 (1989): 311. http://dx.doi.org/10.3367/ufnr.0157.198902c.0311.

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Shklovskiĭ, V. A., and V. M. Kuz'menko. "Explosive crystallization of amorphous substances." Soviet Physics Uspekhi 32, no. 2 (February 28, 1989): 163–80. http://dx.doi.org/10.1070/pu1989v032n02abeh002681.

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Webster, Gregory K., Cynthia A. Pommerening, Whitney W. Harman, Mathew A. Gragg, Jian-Hwa Han, and Daniel J. Taylor. "Exploiting Kinetic Solubility Differences for Low Level Detection of Crystallinity in Amorphous Drug Formulations." Current Pharmaceutical Analysis 16, no. 5 (June 15, 2020): 529–38. http://dx.doi.org/10.2174/1573412915666181210144338.

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Background: Enabling formulations have been implemented by the pharmaceutical industry as an effective tool for keeping Active Pharmaceutical Ingredient (API) in an amorphous state. Upon dosing in the amorphous state, many drugs which fail to demonstrate bioactivity due to the limited solubility and bioavailability of their crystalline form become bioavailable. Purpose: The analytical techniques use today for crystallinity detection are challenged by the sensitivity and robustness needed to achieve a 5% quantitation limit in low dose drug products. Our laboratory has developed a novel procedure capable of meeting this sensitivity and selectivity requirement. This is achieved by exploiting the differences in kinetic solubility of the formulated amorphous and free crystalline forms of API currently being used in dosage form platforms. Methods: Representative amorphous drug formulations were prepared and spiked with varying levels of crystalline drug substances to evaluate the selectivity and recovery of the crystalline drug substance from the product formulation. Kinetic solubility testing using a (i) Particle wetting phase, (ii) Particle suspending/erosion phase, (iii) Sampling time point and (iv) A total recovery determination for the drug substance. Results: The method selectively and quantitatively distinguishes crystalline drug substance from amorphous drug substance for samples spiked from 2.5% to 10% of the nominal label concentration of the API in the dosage form matrix. Conclusion: The kinetic solubility approach reported here achieves sensitive crystallinity quantitation for low drug level amorphous drug formulations at levels not yet achieved by complimentary analytical techniques.

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Sheka, E. F. "Spectroscopy of amorphous substances with molecular structure." Uspekhi Fizicheskih Nauk 160, no. 2 (1990): 263. http://dx.doi.org/10.3367/ufnr.0160.199002c.0263.

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Sheka, E. F. "Spectroscopy of amorphous substances with molecular structure." Soviet Physics Uspekhi 33, no. 2 (February 28, 1990): 147–66. http://dx.doi.org/10.1070/pu1990v033n02abeh002546.

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Fratzl, P., G. Vogl, and S. Klaumünzer. "Small-angle scattering from porous amorphous substances." Journal of Applied Crystallography 24, no. 5 (October 1, 1991): 588–92. http://dx.doi.org/10.1107/s0021889890012225.

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Mikhailov, E., S. Vlasenko, S. T. Martin, T. Koop, and U. Pöschl. "Amorphous and crystalline aerosol particles interacting with water vapor – Part 1: Microstructure, phase transitions, hygroscopic growth and kinetic limitations." Atmospheric Chemistry and Physics Discussions 9, no. 2 (March 20, 2009): 7333–412. http://dx.doi.org/10.5194/acpd-9-7333-2009.

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Abstract. Interactions with water are crucial for the properties, transformation and climate effects of atmospheric aerosols. Here we outline characteristic features and differences in the interaction of amorphous and crystalline aerosol particles with water vapor. Using a hygroscopicity tandem differential mobility analyzer (H-TDMA), we performed hydration, dehydration and cyclic hydration&amp;dehydration experiments with aerosol particles composed of levoglucosan, oxalic acid and ammonium sulfate (diameters ~100–200 nm, relative uncertainties <0.4%, relative humidities <5% to 95% at 298 K). The measurements and accompanying Köhler model calculations provide new insights into particle microstructure, surface adsorption, bulk absorption, phase transitions and hygroscopic growth. The results of these and related investigations lead to the following main conclusions: 1. Many organic substances (including carboxylic acids, carbohydrates and proteins) tend to form amorphous rather than crystalline phases upon drying of aqueous solution droplets. Depending on viscosity and microstructure, the amorphous phases can be classified as glasses, rubbers, gels or viscous liquids. 2. Amorphous organic substances tend to absorb water vapor and undergo gradual deliquescence and hygroscopic growth at much lower relative humidity than their crystalline counterparts. 3. In the course of hydration and dehydration, certain organic substances can form rubber- or gel-like structures (supra-molecular networks) and undergo stepwise transitions between swollen and collapsed network structures. 4. Organic gels or (semi-)solid amorphous shells (glassy, rubbery, ultra-viscous) with low molecular diffusivity can kinetically limit the uptake and release of water by submicron aerosol particles on (multi-)second time scales, which may influence the hygroscopic growth and activation of aerosol particles as cloud condensation nuclei (CCN) and ice nuclei (IN). 5. The shape and porosity of amorphous and crystalline particles formed upon dehydration of aqueous solution droplets depend on chemical composition and drying conditions. The apparent volume void fractions of particles with highly porous structures can range up to ~50% or more (xerogels, aerogels). Void fractions as well as residual water in dried aerosol particles that are not water-free (due to kinetic limitations of drying or stable hydrate formation) should be taken into account in Köhler model calculations of hygroscopic growth and CCN activation. 6. For efficient description of water uptake and phase transitions of amorphous and crystalline organic and inorganic aerosol particles and particle components, we propose not to limit the terms deliquescence and efflorescence to equilibrium phase transitions of crystalline substances interacting with water vapor. Instead we propose the following generalized definitions: Deliquescence is the transformation of a (semi-)solid substance into a liquid aqueous solution, whereby water is absorbed from the gas phase ("liquefaction upon humidification/hydration"). Efflorescence is the transformation of a substance from a liquid aqueous solution into a (semi-)solid phase, whereby water is evaporated ("solidification upon drying/dehydration"). According to these definitions, individual components as well as entire aerosol particles can undergo gradual or prompt, partial or full deliquescence or efflorescence.

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Shimizu, Y., H. Sogabe, and Y. Terashima. "The effects of colloidal humic substances on the movement of non-ionic hydrophobic organic contaminants in groundwater." Water Science and Technology 38, no. 7 (October 1, 1998): 159–67. http://dx.doi.org/10.2166/wst.1998.0289.

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A controlled experimental study of the sorption of colloidal humic substances (humic acid) and a non-ionic hydrophobic organic compound (naphthalene) onto typical inorganic constituents of aquifer solids was performed using four types of model solid phases {i.e., individual model solids (montmorillonite, kaolinite, amorphous aluminosilicate gel, and amorphous iron oxides) and combined model solids (montmorillonite coated by amorphous aluminosilicate gel or iron oxides)}, which are synthesized in the laboratory. The batch experimental results indicated that the sorption of non-ionic hydrophobic organic compounds and colloidal humic substances onto the aquifer solids is significantly influenced by the solid composition. And it was also suggested that the non-ionic hydrophobic organic compounds which have greater hydrophobicity are considered to be sorbed and stabilized by the mobile colloidal humic substances in groundwater, and these colloids may act as a third phase that can increase the amount of compounds that the flow of groundwater can transport. On the other hand, the non-ionic hydrophobic organic contaminants of smaller hydrophobicity may be retarded significantly with the sorption of colloidal humic substances onto the aquifer solids.

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Dissertations / Theses on the topic "Amorphous substances"

1

Atta-Fynn, Raymond. "Theory of localized electron states and novel structural modeling of amorphous silicon /." View abstract, 2005. http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&res_dat=xri:pqdiss&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&rft_dat=xri:pqdiss:3203330.

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Punsalan, David Troy. "A sorption and dilation investigation of amorphous glassy polymers and physical aging." Access restricted to users with UT Austin EID, 2001. http://wwwlib.umi.com/cr/utexas/fullcit?p3035168.

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Saito, Ichitaro. "Amorphous selenium photoelectric devices." Thesis, University of Cambridge, 2012. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.610017.

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Jiang, Yucheng, and 姜昱丞. "Magnetoresistance, photoconductivity and strain effect in the system of magnetically doped amorphous carbon." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2014. http://hdl.handle.net/10722/208021.

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Gabriel, Margaret A. "Electronic defects in amorphous silicon dioxide /." Thesis, Connect to this title online; UW restricted, 2007. http://hdl.handle.net/1773/8553.

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Goldstein, Alexandra Susan. "Computer simulations of amorphous copper-zirconium /." Thesis, Connect to this title online; UW restricted, 1995. http://hdl.handle.net/1773/8629.

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Chieng, Heng Liang Norman, and n/a. "Amorphous drug preparation using ball milling." University of Otago. School of Pharmacy, 2008. http://adt.otago.ac.nz./public/adt-NZDU20081209.162001.

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Polymorphism and crystallinity are now recognised as important issues in drug development. This is shown by the increased amount of research in this area over recent years. In pharmaceutical development milling is an important unit operation for size reduction to improve powder handling, processing and dissolution rate. The aim of this thesis was to investigate the effect of ball milling (and cryo-milling) on the solid state properties, including amorphous drug formation, of pharmaceutical solids. Milling was carried out using an oscillatory ball mill (Mixer Mill MM301, Retsch GmbH & Co., Germany). In cryo-milling the milling jars were immersed in liquid nitrogen for three min before milling. XRPD was used as the main technique to evaluate the milled samples. Ranitidine hydrochloride (RAN) and indomethacin (INDO) were the model drugs used in this study. It was found that upon milling, RAN form 1 converts to RAN form 2 via an amorphous phase. A faster amorphization rate was observed when the crystalline samples were cryo-milled. Amorphous ranitidine hydrochloride was characterized to have a glass transition (T[g]) range of 13 to 30 �C and a crystallization exotherm (T[c]) between 30 and 65 �C. Conversion was found to occur faster when the temperature of the solid powder was greater than the T[c]. Under various storage conditions, similarly, crystallization of the amorphous phase mainly led to RAN form 2. However, some form 1 and amorphous phase was also detected on the XRPD diffractograms. Using partial least squares regression, the amount of solid form components in the ternary RAN mixtures were successfully quantified. RAN form 2 did not convert to form 1 under any milling (including cryo-milling) or storage conditions used in this study. Overall, RAN form 2 was found to be the thermodynamically stable form and the two (RAN) polymorphs are likely to be a monotropic pair. In a co-milling study of INDO and RAN, the two crystalline drugs were successfully converted into a single amorphous phase after 60 min of co-milling in a cold room (4 �C). The T[g] range (26-44 �C) was also characterized for these mixtures. DRIFTS spectra of the co-milled amorphous samples indicated an interaction had occurred between the carboxylic acid carbonyl (HO-C=O) and benzonyl amide (NC=O) of the INDO molecule with the aci-nitro (C=NO₂) of RAN. Depending on the ratio of INDO to RAN, in general, the amorphous mixtures were stable at 4 �C after 30 days of storage. Crystallization was faster when the binary mixtures were stored at higher temperature or contained higher amounts of RAN in the mixture. Although XRPD and DRIFTS suggested an interaction between the two drugs, co-crystal formation was not observed between INDO and RAN. Ball milling can be used to produce amorphous drug. The rate and extent of amorphization is dependent on the milling conditions. A faster rate of amorphization was observed when the crystalline drugs were cryo-milled. Amorphous drug formation can be made either alone or in combination with another crystalline drug. Amorphization could offer a significant improvement on the dissolution profile and the bioavailability of the poorly water soluble drug - indomethacin. Furthermore, ball milling can also be used to produce a homogenous mix between solids. The �goodmix� effect can be used for seed-induced crystallization or, when the XRPD or Raman data were combined with partial least squares regression, to create a reliable calibration model for quantitative analysis.

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Chen, En-Tsung. "On the pressure formation of metallic glasses." Diss., Georgia Institute of Technology, 1989. http://hdl.handle.net/1853/17978.

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Brüning, Ralf. "Reversible structural relaxation in iron based metallic glasses." Thesis, McGill University, 1986. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=65539.

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Lau, King Cheung. "Crystallization of amorphous alloy and the associated changes of properties." access abstract and table of contents access full-text, 2005. http://libweb.cityu.edu.hk/cgi-bin/ezdb/dissert.pl?msc-ap-b21174453a.pdf.

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Thesis (M.Sc.)--City University of Hong Kong, 2005.<br>At head of title: City University of Hong Kong, Department of Physics and Materials Science, Master of Science in materials engineering & nanotechnology dissertation. Title from title screen (viewed on Sept. 1, 2006) Includes bibliographical references.

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Books on the topic "Amorphous substances"

1

Elliott, S. R. Physics of amorphous materials. 2nd ed. Burnt Mill, Harlow, Essex, England: Longman Scientific & Technical, 1990.

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Elliott, S. R. Physics of amorphous materials. 2nd ed. Harlow, Essex, England: Longman Scientific & Technical, 1990.

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Elliott, S. R. Physics of amorphous materials. Burnt Mill, Harlow, Essex, England: Longman Scientific & Technical, 1989.

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F, Thorpe M., and Tichý L. 1944-, eds. Properties and applications of amorphous materials. Dordrecht: Kluwer Academic Publishers, 2001.

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Kaneyoshi, Takahito. Introduction to amorphous magnets. Singapore: World Scientific, 1992.

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Silva, S. R. P. Properties of amorphous carbon. London: IEE, 2003.

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NATO Advanced Study Institute on Amorphous and Liquid Materials (1985 Passo della Mendola). Amorphous and liquid materials: (proceedings of the NATO Advanced Study Institute of 'Amorphous and Liquid Materials', Passo della Mendda (Trentino), Italy, August 26-Sept 7, 1985). Dordrecht: Nijhoff in cooperation with NATO Scientific Affairs Division, 1987.

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8

Minić, D. M. Amorfni materijali. Čačak: Tehnički fakultet, 2001.

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9

Feltz, Adalbert. Amorphous inorganic materials and glasses. Weinheim: VCH, 1993.

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Zallen, Richard. The physics of amorphous solids. New York: Wiley, 1998.

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Book chapters on the topic "Amorphous substances"

1

Lacks, Daniel J. "Energy Landscapes and Amorphous- Amorphous Transitions." In New Kinds of Phase Transitions: Transformations in Disordered Substances, 481–90. Dordrecht: Springer Netherlands, 2002. http://dx.doi.org/10.1007/978-94-010-0595-1_36.

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Kelires, P. C. "Amorphous-Amorphous Phase Transitions in Elemental Group- IV Semiconductors." In New Kinds of Phase Transitions: Transformations in Disordered Substances, 438–47. Dordrecht: Springer Netherlands, 2002. http://dx.doi.org/10.1007/978-94-010-0595-1_33.

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Degtyareva, V. F. "Amorphous Pressure-Induced Alloys." In New Kinds of Phase Transitions: Transformations in Disordered Substances, 504–14. Dordrecht: Springer Netherlands, 2002. http://dx.doi.org/10.1007/978-94-010-0595-1_38.

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Lyapin, A. G., V. V. Brazhkin, E. L. Gromnitskaya, V. V. Mukhamadiarov, O. V. Stal’gorova, and O. B. Tsiok. "Kinetics and Non-Ergodic Nature of Amorphous-Amorphous Transformations under Pressure." In New Kinds of Phase Transitions: Transformations in Disordered Substances, 448–68. Dordrecht: Springer Netherlands, 2002. http://dx.doi.org/10.1007/978-94-010-0595-1_34.

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Koverda, V. P., N. M. Boganov, and V. P. Skripov. "Explosive Crystallization of Amorphous Substances with Fixed Crystallites." In Growth of Crystals, 69–81. Boston, MA: Springer US, 1991. http://dx.doi.org/10.1007/978-1-4615-3660-4_7.

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Klug, D. D., J. S. Tse, V. Shpakov, C. A. Tulk, I. Swainson, E. C. Svensson, and C. K. Loong. "Transformations, Dynamics, and Structures of Amorphous Ices." In New Kinds of Phase Transitions: Transformations in Disordered Substances, 391–402. Dordrecht: Springer Netherlands, 2002. http://dx.doi.org/10.1007/978-94-010-0595-1_29.

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Pichler, H., and C. Schmitt-Riegraf. "Optically isotropic (also pseudo-cubic) minerals and amorphous substances." In Rock-forming Minerals in Thin Section, 35–53. Dordrecht: Springer Netherlands, 1997. http://dx.doi.org/10.1007/978-94-009-1443-8_5.

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Bording, J. K., J. E. Tibballs, and J. Tafto. "From Liquid to Amorphous Germanium by Molecular Dynamics." In New Kinds of Phase Transitions: Transformations in Disordered Substances, 200–207. Dordrecht: Springer Netherlands, 2002. http://dx.doi.org/10.1007/978-94-010-0595-1_15.

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Malenkov, G. G. "Computer Simulation of Supercooled Water and Amorphous Ices." In New Kinds of Phase Transitions: Transformations in Disordered Substances, 423–36. Dordrecht: Springer Netherlands, 2002. http://dx.doi.org/10.1007/978-94-010-0595-1_32.

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Kohl, I., T. Loerting, C. Salzmann, E. Mayer, and A. Hallbrucker. "High-Density Amorphous Ice and its Phase Transition to Ice XII." In New Kinds of Phase Transitions: Transformations in Disordered Substances, 325–33. Dordrecht: Springer Netherlands, 2002. http://dx.doi.org/10.1007/978-94-010-0595-1_24.

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Conference papers on the topic "Amorphous substances"

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Imamura, Koreyoshi, K. Takeda, K. Yamamoto, H. Imanaka, and N. Ishida. "Thermal stability of amorphous sugar matrix, dried from methanol, as an amorphous solid dispersion carrier." In 21st International Drying Symposium. Valencia: Universitat Politècnica València, 2018. http://dx.doi.org/10.4995/ids2018.2018.7716.

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Developing a technique to disperse hydrophobic ingredients homogeneously in a water-soluble solid matrix (solid dispersion) is one of the topics that have been extensively investigated in the pharmaceutical and food industries. Recently, we have devised a novel solid dispersion technique (surfactant-free solid dispersion), in which a preliminarily amorphized sugar was dissolved in an organic media containing hydrophobic component, without using any surface active substances, and then vacuum dried into the amorphous solid mixture [Food Chem., 197 (2016) 1136; Mol. Pharm., 14 (2017) 791]. In this study, the physicochemical properties, especially thermal stability of the surfactant-free amorphous solid dispersion, were investigated. keywords: solid dispersion; amorphous sugar; surfactant-free; vacuum drying; glass transition temperature

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Xu, Yuting, Zhifang Wu, and Qiang Wang. "A Study on Radiation Imaging Mechanism and Characteristics in Different Inspection Systems." In 2021 28th International Conference on Nuclear Engineering. American Society of Mechanical Engineers, 2021. http://dx.doi.org/10.1115/icone28-66127.

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Abstract Radiation imaging, as a key issue in nuclear technology, has received considerable attention in the industry. It is widely used in nuclear medicine, Customs supervision, and many other areas. The objective of this investigation is to get insight into the principle, operation characteristics and image characteristics of radiation imaging. In this paper, an investigation on radiation imaging is conducted on three main inspection systems for Customs supervision, including small X-ray inspection machine, CT baggage inspection system, and large container inspection system. The principle, operation characteristics, evaluation indexes, pseudo-color processing and image characteristics are discussed in detail. The results indicate that the spatial resolution of small X-ray inspection machine is much higher than that of CT baggage/goods inspection system and large container/vehicle inspection system. It is a challenge to identify substances and specific shapes in the case of overlapping for small X-ray inspection system. Moreover, the mechanism of X-ray images is discussed as well. The radiation images are divided into three types, including two-dimensional, pseudo-color, high spatial resolution; two-dimensional, gray, high spatial resolution; three-dimensional, pseudo-color, high density resolution. The further investigation on machine inspection images is suggested to focus on the application environment. For some objects with specific characteristics, such as amorphous, explosive, the CT baggage inspection has much better performance than other systems. The research in this paper reveals the mechanism, parametric effect and imaging characteristics. It could provide a necessary foundation for the follow-up intelligent processing, detection, identification and annotation for radiation imaging in nuclear area. The research on inspection devices could lend strong experience to medical treatment, industry and many other fields.

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Murphy, Colm, Denis Kelliher, and John Davenport. "A Nonlinear Finite Element Inverse Approach to Characterize the Material Properties of Tracheal Cartilage: Preliminary Study." In ASME 2010 Summer Bioengineering Conference. American Society of Mechanical Engineers, 2010. http://dx.doi.org/10.1115/sbc2010-19538.

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Tracheal cartilage is a form of hyaline cartilage. Mature hyaline cartilage is classified by miniature aggregations of chondrocytes implanted in an amorphous matrix of ground substance reinforced by collagen fibres designated as collagen type II. The adjacent layer, the perichondrium, consists of collagen fibers and spindle-shaped cells which are similar to fibroblasts. It has been determined that collagen is a nonlinear material[1], and consequently, tracheal cartilage is also nonlinear. Previous research on tracheal cartilage has treated the material as both linear and nonlinear[2].

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Ultarakova, А., N. Lokhova, and A. Yessengaziyev. "Silica removal from waste of ilmenite concentrate pyrometallurgical processing." In Challenges of Science. Institute of Metallurgy and Ore Beneficiation, Satbayev University, 2021. http://dx.doi.org/10.31643/2021.12.

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The article presents the study results for alkaline leaching of fine ilmenite concentrate dusts from electric smelting. The physical and chemical properties of the dusts were studied using chemical and instrumental analysis methods. The dust composition was determined, X-ray phase analysis showed that the dust sample substance is in the X-ray amorphous state, iron is present in the trivalent state, and silicon is bound to magnesium. The dust sample study using a scanning electron microscope showed that part of the titanium is bound in a hard-to-disclose anasovite encapsulated in amorphous silicon oxide. The leaching study of electric smelting dust with sodium hydroxide solutions included the study of the effect of sodium hydroxide concentration, process duration, temperature, S: L ratio. The optimal conditions for dust leaching from electric smelting of ilmenite concentrate have been established: temperature 80-90 °C, duration 90-120 min, ratio S: L = 1: 5, the concentration of sodium hydroxide solution 110-115 g/dm3. The silicon extraction degree into the solution under these conditions was 77.7%. The behavior of accompanying components of chromium, zinc, iron, and manganese during dust leaching was also studied. X-ray phase analysis of the cake after leaching shows almost complete amorphization of the leached product, the main phase is a solid solution of Fe2O3·TiO2.

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Diaconescu, Emanuel N., Marilena L. Glovnea, and Ovidiu Petrosel. "A New Experimental Technique to Measure Contact Pressure." In STLE/ASME 2003 International Joint Tribology Conference. ASMEDC, 2003. http://dx.doi.org/10.1115/2003-trib-0278.

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A new technique to measure the pressure in a real contact is proposed. One of contacting surfaces is covered, prior to contact establishment, by a special gel. The contact closing removes the excess gel and, during a certain time interval, the contact pressure transforms the entrapped substance in an amorphous solid. In each point, the refractive index of this solid depends on the pressure acting during transformation. After contact opening, the reflectivity of this coating depends on the former contact pressure and it is mapped by aid of a laser profilometer and becomes an indicator of contact pressure. Theoretical considerations show that the gel must possess certain optical parameters for the method to work. Several experimental reported results offer a clear image upon pressure distribution in Hertz point contacts, end effects in finite length line contacts, pressure distribution between rough surfaces and indicate the onset of plastic deformation.

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Suhadi, Elena, Annisa Sylviana, Firman Kurniawansyah, Hikmatun Ni'mah, Himawan Tri Bayu Murti Petrus, Mahfud Mahfud, and Achmad Roesyadi. "Preparation of Sulfonated SiO<sub>2 </sub>Catalyst from Geothermal Sludge Waste for Sago Flour Hydrolysis." In 4th International Seminar on Fundamental and Application of Chemical Engineering. Switzerland: Trans Tech Publications Ltd, 2024. http://dx.doi.org/10.4028/p-8mzrwm.

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Catalyst is a substance that is widely used in chemical reactions to obtain certain products. This study has been focusing on preparing and employing solid catalyst derived from geothermal sludge (GS) as waste material from Dieng Geothermal Power Plant (PLTPB) activity. The methodology of catalyst preparation was extraction of silica from the sludge by alkali solution, followed by gelling formation and acidification with sulfuric acid solution. The prepared catalyst was then applied in hydrolysis reaction to convert sago flour into glucose.Catalyst properties were assessed in term of morphology, crystallinity, surface area, and activity (hydrolysis reaction). Sample analysis confirmed the produced catalyst was amorphous in general, having 127 m2/g of surface area. In addition, the prepared catalyst contained 78 - 79 % of silica, a significant increase - as a result of preparation - from that of raw material sludge which had 33 - 43 % silica. From the catalyst activity test conducted at 120 - 185°C hydrolysis reaction, as much as 50 % of glucose yield could be obtained from sago starch conversion, indicating prospective catalyst performance.Keyword: Sulfonated SiO2, Catalyst, Geothermal Sludge Waste, Sago, Hydrolysis

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Asadizadeh, M., A. Hedayat, L. Tunstall, M. Taboada Neira, J. A. Vega González, and J. W. Verá Alvarado. "Mechanical Properties of Lightweight Aggregates Produced from Mine Tailings via Alkali-Activation." In 57th U.S. Rock Mechanics/Geomechanics Symposium. ARMA, 2023. http://dx.doi.org/10.56952/arma-2023-0838.

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ABSTRACT This study investigated the production of lightweight aggregates (LWAs) from mine tailings (MTs) using an alkali activation approach. The main objective was to reduce the environmental and cost impacts of handling tailings while producing a useful material for the construction industry. The alkali activation process was used to activate the aluminum oxide and silicon dioxide in MTs to produce LWAs, which were then characterized for physical properties. A pelletization technique was practiced, using a disk granulator machine to spray a 10 M NaOH solution on the MTs with a liquid/solid ratio of 0.25. The produced LWAs were cured at temperatures 70 °C±2°C, and the properties of the resulting materials were assessed as a function of the type of fly ash used (class C and F fly ash). Results showed that using Class F fly ash is more successful for making LWAS, and its increasing percentage in the mixture led to increased compressive strength and relative and bulk densities and decreased water absorption and porosity. This study highlights the potential for producing sustainable construction materials from MTs using alkali activation, which could reduce the environmental impacts of MTs while producing useful materials for the construction industry. INTRODUCTION Minerals are in high demand, and as a result, mine tailings (MTs), a byproduct of the mining industry, are produced in high volumes. After the important metals have been extracted from ore through a process called mineral processing, the crushed waste rocks that remain are transferred to the tailings dam. Between 5 and 7 billion tons of tailings are made each year by the mining industry (Qi & Fourie, 2019; Wang et al., 2022). Large volumes of MTs with a high sulfide content can be produced during mining operations, especially from mines with low-grade ore deposits such as gold, and porphyry copper. This can cause several problems including occupation of large areas of land and leaching of contaminants into water sources. Some researchers have looked into ways to mitigate the negative effects of MTs on the environment, such as repurposing them as backfill material (Behera et al., 2021) or utilizing them in the form of supplementary cementitious materials (Ince et al., 2021) or alkali-activated binders (Koohestani et al., 2021). Alkaline activation has been proven as a promising method for production of geopolymers from raw tailings with aluminosilicate contents (Falayi, 2020; Tho-In et al., 2018; Zhang et al., 2021; Zhang et al., 2022a; Zhang, et al., 2022b). Geopolymers are a type of inorganic substance made by alkaline activation of aluminosilicate-rich source materials at temperatures typically below 100 °C (Davidovits, 2020; Zhang et al., 2022b). Aluminosilicate-based geopolymers rely heavily on the Si:Al ratio and are made up of the four cell structures, including sialate (Si:Al = 1), sialate siloxo (Si:Al = 2), sialate disiloxo (Si:Al =3), and sialate-multisiloxo (Si: Al&gt;3). The mechanical properties of geopolymers are controlled by the ratio of Si to Al, and MTs often don't contain sufficient amounts of reactive aluminosilicates (i.e., Si:Al &lt; 2). As a result, improving geopolymerization requires including reactive aluminosilicates and modifying the type of cell structures in alkali-activated materials (AAMs). Extensive studies have been conducted to improve the geopolymer's mechanical properties by adding amorphous aluminosilicates from other sources, such as fly ash (Farina et al., 2018; Jiao et al., 2013; Tian et al., 2020; Zhang et al., 2022b).

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