THE SURFACE ENERGY OF TOBERMORITE

1959 ◽  
Vol 37 (4) ◽  
pp. 714-724 ◽  
Author(s):  
Stephen Brunauer ◽  
D. L. Kantro ◽  
C. H. Weise
Keyword(s):  
Surface Energy ◽  
Room Temperature ◽  
Geometric Mean ◽  
Adsorbed Water ◽  
Tricalcium Silicate ◽  
Dicalcium Silicate ◽  
Total Surface Energy ◽  
Cross Sectional ◽  
Surface Areas ◽  
Negative Surface

The total surface energy (or surface enthalpy) of a calcium silicate hydrate, tobermorite, having the composition of Ca3Si2O7•2H2O, was determined at 23.5 °C. The tobermorite was obtained from the room-temperature hydration of tricalcium silicate, Ca3SiO5, or β-dicalcium silicate, β-Ca2SiO4, two of the most important constituents of portland cements. The hydration reactions were carried out in three different ways, and 14 preparations were obtained. For each preparation the heats of solution in a mixture of nitric acid and hydrofluoric acid were measured at 23.5 °C, and the surface areas were determined by the B.E.T. method, using water vapor at 25 °C as the adsorbate. The cross-sectional area of the adsorbed water molecule was taken to be 11.4 Å2. The surface energy of tobermorite at 23.5 °C was found to be 386 ± 20 ergs/cm2. It is close to the geometric mean of the surface energies of calcium hydroxide and hydrous amorphous silica, previously reported.Nitrogen adsorption did not measure the true surface area of most tobermorite preparations. This was indicated by negative surface energy values in a number of instances.

Active Belite Cement Clinker Produced with Mineral Waste

2012 ◽  
Vol 610-613 ◽  
pp. 2378-2385 ◽  
Author(s):  
Yan Jun Liu ◽  
Yong Chao Zheng
Keyword(s):  
High Temperature ◽  
Room Temperature ◽  
Mechanical Tests ◽  
Tricalcium Silicate ◽  
Dicalcium Silicate ◽  
Cement Industry ◽  
Cement Clinker ◽  
Strength Development ◽  
Belite Cement ◽  
Mineral Waste

This paper presents a laboratory study on active belite cement linker using mineral waste as one of the major raw meal components. The main chemical component of mineral waste employed in this study is silica (SiO2), around 70%. The raw meals were soaked in Muffle Furnace at 1350oC for 10 minutes and 20minutes respectively, then, cooled down to room temperature using air blower. Boron Oxide was used to stabilize high temperature phases of C2S. QXRD analysis indicates that active belite cement clinker has major mineral components consisting of Dicalcium Silicate (C2S), Ferrite (C2 (A0.48F1.52) O5) and trace amount of Tricalcium Silicate (C3S). Among them, Dicalcium silicate is over 85 percent, Ferrite around 10 percent and Tricalcium silicate less than 10 percent. Also, significant amount of high temperature polymorphic C2S was stabilized under room temperature. Among polymorphic belite phases, αH-C2S accounts for around 66% of cement clinker, and αL-C2S for about 22% of cement clinker. Scanning Eαlectronic Microscope (SEM) analysis also shows coαnsiderable round grains of C2S. TGA-DSC spectrum indicated there is no significant phase change while cement clinker was cooling down. Also, the mechanical tests on active belite cement show that active belite cement clinker has a slow strength development at early ages, but rapid strength gain over 70Mpa at 28 days. Thus, this active belite cement clinker demonstrates very promising prospect in sustainable cement industry development.

THE SURFACE ENERGIES OF AMORPHOUS SILICA AND HYDROUS AMORPHOUS SILICA

1956 ◽  
Vol 34 (10) ◽  
pp. 1483-1496 ◽  
Author(s):  
Stephen Brunauer ◽  
D. L. Kantro ◽  
C. H. Weise
Keyword(s):  
Surface Energy ◽  
Amorphous Silica ◽  
Liquid Water ◽  
Bound Water ◽  
Adsorbed Water ◽  
Heat Of Hydration ◽  
Molecular Area ◽  
Surface Energies ◽  
Average Dimension ◽  
Surface Areas

The total surface energies (or, more strictly, surface enthalpies) of amorphous silica and hydrous amorphous silica were determined by measuring the heats of solution in a mixture of nitric acid and hydrofluoric acid of samples having differing specific surface areas and bound water contents, and by measuring the surface areas by the B.E.T. method, using nitrogen as adsorbate. The molecular area of nitrogen was taken to be 16.2 Å2 at 77.3 °K. The surface energy of amorphous silica of zero water content (or the energy of the pure siloxane surface) at 23 °C. was found to be 259 ± 3 ergs/cm.2 The heat of hydration by liquid water of the siloxane surface to silanol surface at 23 °C. was found to be 258.6 ± 13.0 cal./gm. of water. From these two values, with the added assumption that the molecular area of bound water was 25 Å2, the surface energy of hydrous amorphous silica with a completely hydrated surface (or the energy of pure silanol surface) at 23 °C. was calculated to be 129 ± 8 ergs/cm.2 This value is only slightly greater than the surface energy of liquid water. Surface area determinations were also made by water vapor adsorption at 25 °C. The packing of physically adsorbed water appeared to be determined by the geometry of the surface. The cross-sectional area of the adsorbed water molecule was found to be 12.5 Å2. The density of amorphous anhydrous silica was 2.28 to 2.29 gm./cc. Silica particles having an average dimension of 37 Å were dehydrated at lower temperatures and sintered at lower temperatures than particles having an average dimension of 64 Å.

scholarly journals Vapor Phase Adsorption of Water on Hydroxyapatite

1977 ◽  
Vol 56 (12) ◽  
pp. 1437-1448 ◽  
Author(s):  
Hillar M. Rootare ◽  
Robert G. Craig
Keyword(s):  
Adsorbed Water ◽  
Water Vapor Adsorption ◽  
Sectional Area ◽  
Free Energies ◽  
Cross Sectional ◽  
Heats Of Adsorption ◽  
Surface Areas ◽  
Adsorption Of Water ◽  
Enthalpy And Entropy ◽  
Entropy Of Adsorption

Water vapor adsorption isotherms were determined gravimetrically on three hydroxyapatite samples differing in preparation and with surface areas of 70.4, 22.5, and 3.0 M 2/gm, respectively. Heats of adsorption for the first layer of water were found to be 13.3, 13.2, and 13.9 kcallmole on these hydroxyapatites. From repeated thermal desorption and adsorption cycles of water, stepwise adsorption was observed which diminished with each outgassing cycle until it disappeared after the fourth cycle. Cross-sectional area of adsorbed water molecule on hydroxyapatite surface was estimated at 11.5 Å2. Standard free energies, isosteric heats, changes in enthalpy, and entropy of adsorption of water on HAP samples outgassed at 300 C were determined.

Hair cell changes after cationic stimulation of corti's organ

1989 ◽  
Vol 47 ◽  
pp. 798-799
Author(s):  
Cesar D. Fermin ◽  
Hans-Peter Zenner
Keyword(s):  
Organ Of Corti ◽  
Cross Sectional ◽  
Surface Areas ◽  
High K ◽  
Anatomical Arrangement ◽  
Cell Cytosol ◽  
High Concentrations ◽  
K Concentration ◽  
Cell Changes

Contraction of outer and inner hair cells (OHC&IHC) in the Organ of Corti (OC) of the inner ear is necessary for sound transduction. Getting at HC in vivo preparations is difficult. Thus, isolated HCs have been used to study OHC properties. Even though viability has been shown in isolated (iOHC) preparations by good responses to current and cationic stimulation, the contribution of adjoining cells can not be explained with iOHC preparations. This study was undertaken to examine changes in the OHC after expossure of the OHC to high concentrations of potassium (K) and sodium (Na), by carefully immersing the OC in either artifical endolymph or perilymph. After K and Na exposure, OCs were fixed with 3% glutaraldehyde, post-fixed in osmium, separated into base, middle and apex and embedded in Araldite™. One μm thick sections were prepared for analysis with the light and E.M. Cross sectional areas were measured with Bioquant™ software.Potassium and sodium both cause isolated guinea pig OHC to contract. In vivo high K concentration may cause uncontrolled and sustained contractions that could contribute to Meniere's disease. The behavior of OHC in the vivo setting might be very different from that of iOHC. We show here changes of the cell cytosol and cisterns caused by K and Na to OHC in situs. The table below shows results from cross sectional area measurements of OHC from OC that were exposed to either K or Na. As one would expect, from the anatomical arrangement of the OC, OHC#l that are supported by rigid tissue would probably be displaced (move) less than those OHC located away from the pillar. Surprisingly, cells in the middle turn of the cochlea changed their surface areas more than those at either end of the cochlea. Moreover, changes in surface area do not seem to differ between K and Na treated OCs.

TEM sample preparation of wear-tested room-temperature pulsed-laser-deposited thin films of MoS2 by ultramicrotomy

1993 ◽  
Vol 51 ◽  
pp. 1118-1119
Author(s):  
Pamela F. Lloyd ◽  
Scott D. Walck
Keyword(s):  
Thin Films ◽  
Sample Preparation ◽  
Room Temperature ◽  
High Vacuum ◽  
Pulsed Laser ◽  
Ultra High Vacuum ◽  
Wear Testing ◽  
Preparation Technique ◽  
Cross Sectional ◽  
Aerospace Applications

Pulsed laser deposition (PLD) is a novel technique for the deposition of tribological thin films. MoS2 is the archetypical solid lubricant material for aerospace applications. It provides a low coefficient of friction from cryogenic temperatures to about 350°C and can be used in ultra high vacuum environments. The TEM is ideally suited for studying the microstructural and tribo-chemical changes that occur during wear. The normal cross sectional TEM sample preparation method does not work well because the material’s lubricity causes the sandwich to separate. Walck et al. deposited MoS2 through a mesh mask which gave suitable results for as-deposited films, but the discontinuous nature of the film is unsuitable for wear-testing. To investigate wear-tested, room temperature (RT) PLD MoS2 films, the sample preparation technique of Heuer and Howitt was adapted.Two 300 run thick films were deposited on single crystal NaCl substrates. One was wear-tested on a ball-on-disk tribometer using a 30 gm load at 150 rpm for one minute, and subsequently coated with a heavy layer of evaporated gold.

Investigation on a New Hydraulic Cementitious Binder Made from Phosphogypsum

2013 ◽  
Vol 864-867 ◽  
pp. 1923-1928
Author(s):  
Yue Xu ◽  
Jian Xi Li ◽  
Li Li Kan
Keyword(s):  
Compressive Strength ◽  
Fly Ash ◽  
Active Carbon ◽  
High Strength ◽  
Tricalcium Silicate ◽  
Dicalcium Silicate ◽  
Cementitious Material ◽  
Saturation Ratio ◽  
Tricalcium Aluminate ◽  
Cementitious Binder

A new kind of high strength cementitious material is made from phosphogypsum (PG), active carbon and fly-ash. Through the orthogonal research, it was showed that the calcination temperature, retention time, dosage of active carbon and fly ash on the compressive strength of cementitious binder are the most important. The result also showed that, in the conditions of temperature 1200°C, time retention 30 min, dosage of active carbon 10%, dosage of fly ash 5%, the compressive strength of the cementitious material for 3d and 28d could reach to 46.35MPa and 92.70MPa, the content of sulfur trioxide was 11.60% accordingly. A lot of active mineral materials, such as dicalcium silicate, tricalcium silicate, tricalcium aluminate were formed in the calcination. The C-S-H gel, calcium hydroxide and ettringite were found in 3d and 28d hydrates. It is found that the lime saturation ratio and silica modulus need to be control between 0.40~0.65 and 4~8 in order to produce high strength cementitious material.

scholarly journals Urinary Concentrations of Metals and Metalloids in Malaysian Adults

2021 ◽  
Author(s):  
Zurahanim Fasha Anual ◽  
Noraishah Mohammad Sham ◽  
Rashidah Ambak ◽  
Fatimah Othman ◽  
Rafiza Shaharudin
Keyword(s):  
Rural Areas ◽  
Urban Areas ◽  
Inductively Coupled Plasma ◽  
Geometric Mean ◽  
Urine Samples ◽  
Cross Sectional ◽  
Metals And Metalloids ◽  
High Exposure ◽  
Academic Qualification ◽  
Metal Levels

AbstractExposure to environmental pollutants in humans can be conducted through direct measurement of biological media such as blood, urine or hair. Assessment studies of metals and metalloids in Malaysia is very scarce although cross-sectional nationwide human biomonitoring surveys have been established by the USA, Canada, Germany, Spain, France, and Korea. This study aims to assess urinary metal levels namely cadmium (Cd), nickel (Ni), lead (Pb) and arsenic (As) among Malaysian adults. This was a cross-sectional study involving 1440 adults between the age of 18 and 88 years old. After excluding those with 24 h urine samples of less than 500 ml, urine creatinine levels < 0.3 or > 3.0 g/L and those who refuse to participate in the study, a total of 817 respondents were included for analysis. A questionnaire with socio-demographic information such as age, gender, occupation, ethnic, academic qualification and medical history was administered to the respondents. Twenty-four-hour urine samples were collected in a container before being transported at 4 °C to the laboratory. Samples were then aliquoted into 15 ml tubes and kept at − 80 °C until further analysis. Urine was diluted ten-fold with ultrapure water, filtered and analysed for metals and metalloids using Inductively Coupled Plasma-Mass Spectrometry (ICP-MS). The geometric mean of urinary As, Ni, Cd and Pb concentrations among adults in Malaysia was 48.21, 4.37, 0.32, and 0.80 µg/L, respectively. Males showed significantly higher urinary metal concentrations compared to females for As, Cd and Pb except for Ni. Those who resided in rural areas exhibited significantly higher As, Cd and Pb urinary concentrations than those who resided in urban areas. As there are no nationwide data on urinary metals, findings from this study could be used to identify high exposure groups, thus enabling policy makers to improve public health strategically.

scholarly journals Urinary Paraben Concentration and Its Association with Serum Triglyceride Concentration in 2013-2014 NHANES Participants: A Cross-Sectional Study

2020 ◽  
Vol 2020 ◽  
pp. 1-6 ◽  
Author(s):  
Rebecca Pazos ◽  
Cristina Palacios ◽  
Adriana Campa
Keyword(s):  
Geometric Mean ◽  
Serum Triglyceride ◽  
Health Impact ◽  
Cross Sectional Study ◽  
Urinary Concentration ◽  
Sectional Study ◽  
Cross Sectional ◽  
Endocrine Disrupting ◽  
Serum Triglyceride Concentration ◽  
Hispanic White

Background. Alkyl esters of para-hydroxybenzoic acid, colloquially known as parabens, are types of preservatives found in multiple foodstuffs, pharmaceuticals, and personal care products to which Americans are exposed daily. It is unclear if parabens exhibit endocrine-disrupting properties. Parabens may interact with triglycerides in adipose tissue and impact lipid metabolism. Objective. To evaluate the association between urinary paraben concentrations and serum triglyceride concentrations. Design. A cross-sectional study. Setting. The Mobile Examination Centers affiliated with 2013-2014 NHANES. Participant(s). 827 adults (20 years or older) affiliated with the 2013-2014 NHANES. Intervention(s). None. Main Outcome Measure(s). Triglyceride levels were associated with urinary paraben concentrations (methyl, ethyl, and propyl) using a hierarchical multiple regression, adjusting for ethnicity/race, gender, BMI, and age. Unadjusted results are also reported. Results. The geometric mean of the urinary concentration of methylparaben, ethylparaben, and propylparaben was 57.100, 2.537, and 6.537 ng/ml, respectively. Triglyceride concentrations were inversely associated with methylparaben (β = −0.092, P=0.07), ethylparaben (β = −0.066, P=0.045), and propylparaben (β = −0.076, P=0.025). Being female, non-Hispanic White, and non-Hispanic Black were associated with decreasing triglyceride levels in the presence of methylparaben, ethylparaben, and propylparaben, and age, BMI, and being male were associated with increasing circulating triglycerides. Conclusion. Despite the potential detrimental effects of parabens on triglycerides, our results suggest that urinary excretions of methylparaben, ethylparaben, and propylparaben are associated with lower concentrations of circulating triglycerides in certain populations. Further research is needed to confirm the mechanisms and health impact of this relationship.

scholarly journals A cross-sectional survey assessing the influence of theoretically informed behavioural factors on hand hygiene across seven countries during the COVID-19 pandemic

2021 ◽  
Vol 21 (1) ◽  
Author(s):  
K. A. Schmidtke ◽  
K. G. Drinkwater
Keyword(s):  
South Africa ◽  
Saudi Arabia ◽  
United Kingdom ◽  
Hand Hygiene ◽  
Behaviour Change ◽  
Surface Cleaning ◽  
Behaviour Change Techniques ◽  
Cross Sectional ◽  
Surface Areas ◽  
The United Kingdom

Abstract Background Human hygiene behaviours influence the transmission of infectious diseases. Changing maladaptive hygiene habits has the potential to improve public health. Parents and teachers can play an important role in disinfecting surface areas and in helping children develop healthful handwashing habits. The current study aims to inform a future intervention that will help parents and teachers take up this role using a theoretically and empirically informed behaviour change model called the Capabilities-Opportunities-Motivations-Behaviour (COM-B) model. Methods A cross-sectional online survey was designed to measure participants’ capabilities, opportunities, and motivations to [1] increase their children’s handwashing with soap and [2] increase their cleaning of surface areas. Additional items captured how often participants believed their children washed their hands. The final survey was administered early in the coronavirus pandemic (May and June 2020) to 3975 participants from Australia, China, India, Indonesia, Saudi Arabia, South Africa, and the United Kingdom. Participants self-identified as mums, dads, or teachers of children 5 to 10 years old. ANOVAs analyses were used to compare participant capabilities, opportunities, and motivations across countries for handwashing and surface disinfecting. Multiple regressions analyses were conducted for each country to assess the predictive relationship between the COM-B components and children’s handwashing. Results The ANOVA analyses revealed that India had the lowest levels of capability, opportunity, and motivation, for both hand hygiene and surface cleaning. The regression analyses revealed that for Australia, Indonesia, and South Africa, the capability component was the only significant predictor of children’s handwashing. For India, capability and opportunity were significant. For the United Kingdom, capability and motivation were significant. Lastly, for Saudi Arabia all components were significant. Conclusions The discussion explores how the Behaviour Change Wheel methodology could be used to guide further intervention development with community stakeholders in each country. Of the countries assessed, India offers the greatest room for improvement, and behaviour change techniques that influence people’s capability and opportunities should be prioritised there.

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