Effects of Compression During Formation on the Mechanical Strengths and Physical Properties of Composite Hydroxylapatite/Plaster Implants for Bone Reconstruction

1987 ◽  
Vol 110 ◽  
Author(s):  
K. Cowden ◽  
B. Giammara ◽  
N. Georgiade ◽  
R. Noecker ◽  
J. Hanker
Keyword(s):  
Glass Plate ◽  
Potassium Sulfate ◽  
Surgical Reconstruction ◽  
Hardness Tester ◽  
Setting Times ◽  
Excess Water ◽  
Surgical Implantation ◽  
Mechanical Strengths ◽  
Implantation Procedure ◽  
Scanning Electron

AbstractComposite hydroxylapatite/plaster of Paris implants, preformed or formed during the surgical implantation procedure, are undergoing study for the surgical reconstruction of craniofacial bones. It is frequently necessary to accelerate setting times of the hydroxylapatite/plaster (HA/PP) mixtures by the addition of potassium sulfate; in many of these cases rapid delivery of the moistened implant mixture to the surgical site may be achieved by employing a non-tapered syringe with a plunger. This device can facilitate implantation of quick-setting moistened mixtures through soft tissue tunnels or small incisions, and can result in a less invasive surgical procedure. During experimental surgery it was found beneficial to effect maximum compression of the moistened HA/PP mixture against a sterile glass plate prior to its extrusion from the cylinder. This resulted in elimination of excess water from the mixture. Discs formed from compressed mixtures showed greater mechanical or breaking strengths after setting than discs formed without prior compression when evaluated with a Stokes Hardness-Tester. Examination by light and scanning electron microscopy confirmed the greater compactness of the compressed mixtures.

Effects of compression during formation on the microstructure of composite hydroxylapatite/plaster implants for bone reconstruction

1988 ◽  
Vol 46 ◽  
pp. 750-751
Author(s):  
J. Hanker ◽  
K. Cowden ◽  
R. Noecker ◽  
P. Yates ◽  
N. Georgiade ◽  
...  
Keyword(s):  
Cosmetic Surgery ◽  
Glass Plate ◽  
Surgical Reconstruction ◽  
Equal Weight ◽  
Sintered Ceramic ◽  
Setting Times ◽  
Excess Water ◽  
Mixture Prior ◽  
Mechanical Strengths ◽  
Calcium Sulfate Hemihydrate

Composites of plaster of Paris (PP) and hydroxylapatite (HA) particles are being applied for the surgical reconstruction of craniofacial bone defects and for cosmetic surgery. Two types of HA particles are being employed, the dense sintered ceramic (DHA) and the porous, coralline hydroxylapatite (PHA) particles. Excess water is expressed out of the moistened HA/PP mixture prior to implantation and setting by pressing it in a non-tapered syringe against a glass plate. This results in implants with faster setting times and greater mechanical strengths. It was therefore of interest to compare samples of the compressed versus noncompressed mixtures to see whether or not any changes in their microstructure after setting could be related to these different properties.USG Medical Grade Calcium Sulfate Hemihydrate (which has the lowest mortar consistency of any known plaster) was mixed with an equal weight of Interpore 200 particles (a commercial form of PHA). After moistening with a minimum amount of water, disc-shaped noncompressed samples were made by filling small holes (0.339 in. diameter x 0.053 in. deep) in polypropylene molds with a microspatula.

Mechanical Strength Improvement of Apatite Cement Using Hydroxyapatite/Collagen Nanocomposite

2016 ◽  
Vol 720 ◽  
pp. 167-172 ◽  
Author(s):  
Arief Cahyanto ◽  
Kanji Tsuru ◽  
Kunio Ishikawa ◽  
Masanori Kikuchi
Keyword(s):  
Fracture Surface ◽  
Mechanical Strength ◽  
Setting Time ◽  
Control Group ◽  
Scanning Electron Micrographs ◽  
Setting Times ◽  
Apatite Cement ◽  
Xrd Patterns ◽  
Mechanical Strengths ◽  
Scanning Electron

The combination of tetracalcium phosphate (TTCP; Ca4(PO4)2O) and dicalcium phosphate anhydrous (DCPA; CaHPO4) which are known as one system of apatite cements already used in the medical and dental application. In spite of several advantages of apatite cements, such as self-setting ability and biocompatibility, their mechanical strengths are still low. The aim of this study is to improve the mechanical strength of the TTCP-DCPA apatite cement using the hydroxyapatite/collagen nanocomposite (HAp/Col). The apatite cement powder was prepared using an equimolar TTCP and DCPA with addition of 10% and 20% of the HAp/Col. That without the HAp/Col was used as a control group. Each group was mixed with 1 mol/L Na1.8H1.2PO4 aqueous solution at powder/liquid ratio of 0.5 and hardened at 37°C and 100 % of relative humidity for 24 hours. A setting time of the cement was evaluated using Vicat needle according to ISO 1566 for dental zinc phosphate cements. Morphology of the cements set were observed by the scanning electron microscopy (SEM), and crystalline phases were identified by the powder X-Ray diffractometry (XRD). The mechanical strength of the cement set was evaluated by the diametral tensile strength (DTS). The setting times of cements were the shortest for the cement with HAp/Col and the longest for the control. XRD patterns of the cement at 24 hours after mixing revealed that all cements changed into apatite from the mixture of TTCP and DCPA. The DTSs of cements were the highest for the cement with 20% HAp/Col and the lowest for the control with significant differences between the cement with 20 % HAp/Col and respective other two cements. The scanning electron micrographs of the surface and fracture surface of the cements suggested that the cement with HAp/Col showed denser structure in comparison to the control and the HAp/Col fibers and/or sheets covered the fracture surface. The HAp/Col would act as reinforcement fibers as well as an adhesive of apatite granules formed by the reaction between TTCP and DCPA. The setting time and mechanical strength of apatite cement was statistically significant improved by adding 20% HAp/Col.

Effects of sterilization modes on the mechanical strengths of plaster of paris implants

1989 ◽  
Vol 47 ◽  
pp. 890-891
Author(s):  
K. Cowden ◽  
B. Giammara ◽  
T. Devine ◽  
J. Hanker
Keyword(s):  
Gamma Radiation ◽  
Calcium Sulfate ◽  
Significant Loss ◽  
Potassium Sulfate ◽  
Limiting Factors ◽  
Radiation Sterilization ◽  
Plaster Of Paris ◽  
Hardness Tester ◽  
Dry Heat ◽  
Calcium Sulfate Hemihydrate

Plaster of Paris (calcium sulfate hemihydrate, CaSO4. ½ H2O) has been used as a biomedical implant material since 1892. One of the primary limiting factors of these implants is their mechanical properties. These materials have low compressive and tensile strengths when compared to normal bone. These are important limiting factors where large biomechanical forces exist. Previous work has suggested that sterilization techniques could affect the implant’s strength. A study of plaster of Paris implant mechanical and physical properties to find optimum sterilization techniques therefore, could lead to a significant increase in their application and promise for future use as hard tissue prosthetic materials.USG Medical Grade Calcium Sulfate Hemihydrate Types A, A-1 and B, were sterilized by dry heat and by gamma radiation. Types A and B were additionally sterilized with and without the setting agent potassium sulfate (K2SO4). The plaster mixtures were then moistened with a minimum amount of water and formed into disks (.339 in. diameter x .053 in. deep) in polyethylene molds with a microspatula. After drying, the disks were fractured with a Stokes Hardness Tester. The compressive strengths of the disks were obtained directly from the hardness tester. Values for the maximum tensile strengths σo were then calculated: where (P = applied compression, D = disk diameter, and t = disk thickness). Plaster disks (types A and B) that contained no setting agent showed a significant loss in strength with either dry heat or gamma radiation sterilization. Those that contained potassium sulfate (K2SO4) did not show a significant loss in strength with either sterilization technique. In all comparisons (with and without K2SO4 and with either dry heat or gamma radiation sterilization) the type B plaster had higher compressive and tensile strengths than that of the type A plaster. The type A-1 plaster however, which is specially modified for accelerated setting, was comparable to that of type B with K2SO4 in both compressive and tensile strength (Table 1).

Pervaporation Dehydration of Isopropanol–Water Mixtures Using Chitosan Zeolite–A Membranes

2012 ◽  
Author(s):  
Mohd. Ghazali Mohd. Nawawi ◽  
Le T. Ngoc Tram
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Glass Plate ◽  
Homogeneous Solution ◽  
Water Mixture ◽  
Zeolite A ◽  
Feed Concentration ◽  
Modified Chitosan ◽  
Chitosan Membranes ◽  
Scanning Electron

Kajian pervaporasi (PV) penyahidratan isopropanol (IPA) menggunakan membran kitosan terubahsuai telah dijalankan. Membran disediakan daripada kitosan dan diubahsuai menggunakan zeolite–A. Zeolit–A yang diketahui beratnya ditambahkan ke dalam pelarut berasid dan diaduk untuk menghasilkan larutan homogen. Kepingan kitosan kemudian ditambahkan ke dalam larutan tersebut dan diaduk semalaman. Pelbagai nisbah zeolit–A dan kitosan daripada 1:20 hingga 1:2 digunakan untuk menghasilkan membran kitosan terubahsuai. Larutan kitosan–zeolit–A dituangkan ke atas plat kaca dan dikeringkan pada suhu bilik. Membran yang dikeringkan kemudian dirawat dengan larutan alkali dan dibasuh di dalam air ternyahion. Sifat hidrofilik membran dikaji melalui ujian pengembungan. Ujian dijalankan dalam campuran 90 wt.% IPA–air. Keputusan menunjukkan bahawa darjah pengembungan berkurangan dengan penambahan zeolit–A. Sifat mekanikal membran dikaji untuk kekuatan tegangan dan pemanjangan pada takat putus. Kemudian, membran tersebut dikaji untuk pemisahan campuran IPA–air pada tekanan 720 mmHg di bawah vakum. Kepekatan suapan diubah daripada 0 hinga 95 wt.% IPA dan suhu suapan diubah daripada 30 hingga 70°C. Keputusan menunjukkan bahawa nisbah 1:8 antara zeolit dan kitosan menghasilkan kombinasi terbaik untuk mengubahsuai membran bagi pemisahan campuran IPA–air. Struktur morfologi membran kitosan–zeolit–A dengan nisbah 1:8 dan 1:2 berat zeolit–A/berat kiotsan dikaji menggunakan Scanning Electron Microscopy (SEM). Keputusan menunjukkan bahawa membran yang dihasilkan adalah padat dan tiada liang dapat diperhatikan. Penambahan zeolit tidak mengubah struktur membran. Kata kunci: Pervaporasi, penyahidratan, membrane, kitosan, zeolite-A, isopropanol Pervaporation (PV) dehydration of isopropanol (IPA) using modified chitosan membranes was studied. The membranes were prepared from chitosan and modified by using zeolite–A. Pre–weighed amount of zeolite–A was added into acidic solvent and stirred to produce homogeneous solution. Chitosan flakes were then added into the solution and stirred overnight. Various ratios of zeolite–A and chitosan from 1:20 to 1:2 were used to produce the modified chitosan membranes. The chitosan–zeolite A solution was casted on a glass plate and dried at room temperature. The dried membranes were treated with alkaline solution and thoroughly washed in deionized water. The hydrophilicity of the membranes was studied through the swelling test. The test was carried out in a 90 wt% IPA–water mixture. The result showed that the degree of swelling decreased with the increase of the amount of zeolite–A. The mechanical properties of membranes were also tested for the tensile strength and elongation at break. Then, the membranes were investigated for the PV separation of IPA–water mixtures at the permeate pressure of 720 mmHg under vacuum. The feed concentration was varied from 0 to 95 wt% IPA, and the feed temperature was varied from 30 to 70°C. The results showed that the ratio 1:8 of zeolite–A and chitosan produced the best combination to modify the membrane for the separation of water–IPA mixtures. The structural morphologies of the chitosan filled zeolite–A membranes with ratio 1:8 and 1:2 wt zeolite–A/wt chitosan was studied under Scanning Electron Microscopy (SEM). The results showed that the membranes were dense, and no pores were visible. The addition of the zeolite did not alter the structure of the membranes. Key words: Pervaporation, dehydration, membrane, chitosan, zeolite-A, isopropanol

scholarly journals Mechanical Strengths of Sawdust-Ash-Admixed Gum Arabic Concrete

2021 ◽  
Vol 8 (1) ◽  
pp. 12-29
Author(s):  
Augustine Uchechukwu Elinwa
Keyword(s):  
Cement Content ◽  
Gum Arabic ◽  
Strength Ratio ◽  
Design Strength ◽  
Conventional Concrete ◽  
Cement Material ◽  
Cement Ratio ◽  
Setting Times ◽  
Concrete Mixtures ◽  
Mechanical Strengths

Gum Arabic and sawdust ash were used both as an emulsifier admixture and supplementary cement material to address some of the gaps between pozzolanic and conventional concretes. Four concrete mixtures of 1: 2.24: 2.71, with a water-cement ratio of 0.5, and cement content of 370 kg/m3, was used. The concrete mixtures were designated as M-00, M-00GA, M-10GAS, and M-30GAS, signifying the control, control with gum Arabic (GA), and mix with both gum Arabic and sawdust ash (GAS), respectively. The dosage was 0.5 % of GA and the SDA replacement by wt. % was at 10 % and 30 %, respectively. The concrete samples were cured for 90 days, and tested for mechanical strengths. The results showed that adding GA alone to concrete mixture improved the mechanical strengths of the concrete and the gum Arabic acted like an accelerator. When both GA and SDA were used together in the dosage of 0.5 % with 10 % and 30 % proportions respectively, the mechanical strengths of the concrete decreased. The findings also reported that the two-third strength ratio at 28-days of curing which is used for the conventional concrete in stripping the formwork, may not be appropriate for use on pozzolanic concrete. This is because of the delay in setting times and thus, attaining the required design strength. Therefore, it is proposed to be taken at an age beyond 28 days of curing to carter for the pozzolanic effects which starts well above 28-days.

IMPROVED NITRIDING CAPABILITY OF NONALLOYED STEELS ASSISTED WITH ACTIVE SCREEN PLASMA TREATMENT

2019 ◽  
Vol 27 (03) ◽  
pp. 1950118 ◽  
Author(s):  
M. NAEEM ◽  
H. A. RAZA ◽  
M. SHAFIQ ◽  
FARHAT SHABBIR ◽  
JAVED IQBAL ◽  
...  
Keyword(s):  
Plasma Treatment ◽  
Cost Effective ◽  
Additional Treatment ◽  
X Ray Diffraction ◽  
X Ray ◽  
Hardness Tester ◽  
Polarization Test ◽  
Pin On Disc ◽  
Scanning Electron ◽  
Active Screen

The nonalloyed steels are very cost-effective, but their usefulness in numerous applications is imbedded due to low mechanical strength. The strength of several steels can be improved by nitriding; however, nonalloyed steels are not suitable. They can be nitrided by introducing special nitriding alloys (like chromium, aluminum, etc.) during manufacturing or some interlayer deposition, but it is quite expensive. The aim of this study is to improve nitriding capability of nonalloyed steels without any additional treatment. This is done by using alloyed stainless steel active screen in active screen plasma treatment, which provides an adequate amount of chromium to form stable and hard nitrides. The processed samples are characterized by X-ray diffraction, scanning electron microscope, energy dispersive spectroscopy, pin-on-disc wear tester, hardness tester and potentiodynamic polarization test.

Synthesize and Characterization Zr-Al-Si Post through Eggshell Membrane Strengthening with PMMA Matrix

2016 ◽  
Vol 696 ◽  
pp. 85-88
Author(s):  
Niko Eka Putra ◽  
Yosa Fendra ◽  
Denny Nurdin ◽  
Bambang Sunendar Purwasasmita
Keyword(s):  
Electron Microscope ◽  
Scanning Electron Microscope ◽  
Polymethyl Methacrylate ◽  
Sol Gel ◽  
Eggshell Membrane ◽  
Gel Method ◽  
Sol Gel Method ◽  
Three Point Bending ◽  
Hardness Tester ◽  
Scanning Electron

Zr-Al-Si posts were successfully synthesized using biotemplate of eggshell membrane by sol-gel method and strengthening with matrix of polymethyl methacrylate (PMMA). The dental posts made were analyzed with the scanning electron microscope (SEM), three point bending and microvickers hardness tester. There are two methods used to synthesized Zr-Al-Si posts, with calcination and without calcination. The synthesized mechanism is discussed here.

Investigation on Recovery and Recrystallization of Al-Si-Al2O3 Composites

2013 ◽  
Vol 813 ◽  
pp. 345-350
Author(s):  
Xiong Wei Wang ◽  
Xiao Song Jiang ◽  
De Gui Zhu ◽  
Luo Zhang
Keyword(s):  
Electron Microscopy ◽  
Heat Treatment ◽  
Optical Microscope ◽  
In Situ Synthesis ◽  
Recrystallization Temperature ◽  
Recrystallization Behavior ◽  
Micro Hardness ◽  
Hardness Tester ◽  
Scanning Electron

Al-Si-Al2O3 composites were prepared by powder metallurgy with in-situ synthesis technology. The recovery and recrystallization behavior of Al-Si-Al2O3 composites which underwent compression and then heat-treatment under different temperature were studied using micro-hardness tester, optical microscope (OM) and scanning electron microscopy (SEM) . The results showed that the hardness of composites increased dramatically after compression, and the sample containing 5wt% Si was increasing more evidently than the sample including 10wt%Si. Heat treatment gradually eliminated work hardening; meanwhile the fact that the hardness of composites trended to decline greatly when subjected to annealing suggested occurrence of recovery and recrystallization inside the composites. Recrystallization nucleation preferentially took place in the region near the particle, while the growth of recrystallized grains can also be hindered owning to the pining effect of particles. Depending on the analysis of microstructure and microhardness, it can be concluded that the recrystallization temperature of Al-wt.5%Si-Al2O3 composites was 500°C and the Al-wt.10%Si-Al2O3 composites was 525°C.

Effect of Coating Removal by Induction Heating on the Microstructure and Properties of Deck Steel

2016 ◽  
Vol 723 ◽  
pp. 517-521
Author(s):  
Jia Hui Cai ◽  
Xiao Feng Sun ◽  
Ji Qiu
Keyword(s):  
Electron Microscope ◽  
Cross Section ◽  
Induction Heating ◽  
Micro Hardness ◽  
Untreated Sample ◽  
Hardness Tester ◽  
Before And After ◽  
Coating Removal ◽  
Carbide Particles ◽  
Scanning Electron

Deck steel with anti-skid coating is treated by induction heating for coating removal. The microstructure of cross-section before and after coating removal is observed by metallographic microscope and scanning electron microscope. Z-direction micro-hardness of cross-section before and after coating removal is tested by micro-hardness tester. Results show that the softening layer of about 3 mm, which the average micro-hardness of the layer is 244 HV, is formed on the surface of the sample. The micro-hardness decreases by 3.5% compared with the untreated sample. Coating removal by induction heating will not have an impact on the metallographic structure. But carbide particles will be precipitated at the grain boundary. At last, the influence of induction heating on the performance of deck steel is briefly analyzed.

Interaction between Yttria Fully Stabilized Zirconia or Yttria-Zirconia Blended Face-Coat with Ti6Al4V during Investment Casting

2014 ◽  
Vol 1019 ◽  
pp. 302-310 ◽  
Author(s):  
Kalenda Mutombo ◽  
Christina Kgomo ◽  
P. Rossouw
Keyword(s):  
Electron Microscopy ◽  
Xrd Analysis ◽  
Experimental Results ◽  
X Ray Diffraction ◽  
Stabilized Zirconia ◽  
X Ray ◽  
Hardness Tester ◽  
Alpha Case ◽  
Face Coat ◽  
Scanning Electron

The interaction between the Ti6Al4V alloy and the mould materials was investigated. The alpha-case was characterized by Vickers hardness tester, optical and scanning electron microscopy equipped with electron dispersive X-ray spectrometry (EDX). X-ray diffraction (XRD) analysis was performed on as cast and on YFSZ or YZ-Blended face-coats. From the experimental results, a distinct alpha-case formation was revealed. The YFSZ led to a thicker and harder alpha-case than the YZ-Blended face-coat. The EDX revealed the presence of Zr and Si elements in both alpha-cases. Therefore, from experimental results and thermodynamic calculations, pure ZrO2and SiO2may react with Ti.

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